> ## Documentation Index > Fetch the complete documentation index at: https://docs.cfo.ai/llms.txt > Use this file to discover all available pages before exploring further. # Build your first Model > A 15-minute lesson for new users: tell Ari about your business, watch it build a Model, check a number, change an assumption, and take the change back. In this lesson we build a first Model of your business with Ari, your AI finance coworker. By the end you will have a set of Pages that forecast your next 12 months, and you will have traced one number to its source, changed one assumption, and taken the change back. You need about 15 minutes, a payment card for the free trial, and a few facts you know about your business: what you sell, roughly what you charge, how many people you employ, and how much cash you have. You can start from a description, from your current spreadsheet, or from your accounting system; a description is fastest and works for everyone. > [!NOTE] > > Already signed up and the starting card is gone? Press **⌘ /** (**Ctrl /** on Windows and Linux) to start a new chat, and paste the message from step 2 into the message box. **1. Sign up and open your workspace** Go to [app.cfo.ai](https://app.cfo.ai) and sign up with **Continue with Google**, **Sign in with Microsoft**, or your work email and the six-digit code cfo.ai sends you. When you sign up, cfo.ai asks you to start the 14-day free trial: choose a plan, select **Start free trial**, and add a card. Nothing is charged until the trial ends, and you can cancel any time before then. See [Start a trial or choose a plan](/guides/choose-a-plan.md). A new workspace opens on a chat named **Welcome**. Notice three things: Ari's greeting at the top, a short brief about your company once Ari finishes its research, and a starting card docked above the message box. The card asks **Where would you like to start?** **2. Tell Ari about your business** On the starting card, choose **My business**. The card then asks **What should I work from?** Pick the tab that matches what you have. The rest of the lesson works the same way for all three. **Describe it** Choose **I want to type or upload context**, and type a few sentences like these, with your own details: > We sell \[an annual software subscription] to \[small accounting firms] for about \[\$6,000 a year]. Last month revenue was about \[\$80,000]. We have \[9] employees and about \[\$1.2 million] in the bank. Build a 12-month model so I can see how long our cash lasts. You do not need exact numbers. Ari labels every number you did not give it as an assumption you can change later. Select **Get started**. **Upload your model** Choose **Upload an existing model**, attach your workbook, such as an Excel file, and select **Get started**. Ari rebuilds it in cfo.ai. For a large workbook, see [Import an existing spreadsheet model](/guides/import-a-spreadsheet-model.md). **Connect your books** Choose **Connect my data** and select **Get started**. Ari opens the list of sources; pick your accounting system and approve access in the window that opens. You need administrator access to that system. Ari builds your first Model when the data has loaded, which can take from minutes to hours for a long history, and tells you in this chat when it is ready. See [Connect your accounting system](/guides/connect-accounting.md). Notice that your answers appear in the chat as your message, and Ari starts working on them. > [!NOTE] > > To try cfo.ai with an example business instead of your own, choose **Something hypothetical** on the starting card, then **A business like mine**, or type the kind of business you want. The rest of the lesson works the same way. **3. Watch Ari work** Ari's steps collect in an **Activity** group under your message. For a larger build, Ari first shows a plan card listing the assumptions it intends to use. Read them, change any that are wrong, and select **Build it**. Notice the sidebar. A **Model** section appears with the first Page Ari builds, and more Pages join it one at a time. You can open the first Page while Ari works on the next. **4. Open the first Page** Select the first Page in the sidebar. A Page is a report made of blocks. Most of what you see are Table blocks: rows such as Revenue and Cash, with months across the top. Notice that the numbers are live: the Model calculates each one from your assumptions, so a changed assumption updates every number that uses it. **5. Trace a number you already know** Find a number you already know, such as last month's revenue or your cash balance. Right-click the cell and choose **Mention cell in chat**. The cell appears in the message box. Ask: > Where does this number come from? Show me the formula. Ari explains where the value came from, such as your message, your workbook, or your accounting data, and shows the formula behind any number calculated from it. If a number is wrong, tell Ari the right one. **6. Change an assumption** Ask Ari to change something you might really decide: > Hire two more engineers starting in \[March] at \[\$150,000] a year each, and show what happens to cash. Watch the Page. Notice that Ari's edit plays out on the table, and every number that depends on the new hires changes: payroll, expenses, and the cash balance in each later month. **7. Take the change back** Select the clock icon in the Page header to open **Version history**. Every change to the Model is listed, newest first, with who made it and when. Ari's hiring change is at the top. Point at that entry, select its **…** actions button, and choose **Undo this change**. Notice that the two hires disappear and cash returns to what it was. Nothing you or Ari try in the Model is permanent by accident. ## What you built You have a Model of your business: Pages built from your own description, a number you traced to its source, and an assumption you changed and took back. That loop of asking, checking, and changing is how you will work with Ari every day. ## Next steps * Swap Ari's estimates for your books: [Replace estimates with your real numbers](/guides/switch-to-real-numbers.md). * Already have a model in a spreadsheet? [Import it](/guides/import-a-spreadsheet-model.md). * Keep going with [Your first week](/tutorials/first-week.md): one short lesson a day. * Learn how the pieces fit together in [How cfo.ai works](/concepts/how-cfoai-works.md). This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.