Form 1040 is automatically filled out for you based on your responses within the Federal and My Info sections of TurboTax. If there is a specific area you would like to add to or update you would first determine whether it is personal information, income, or deductions and credits, and then find the correct subsection.
For example, to add a W-2 you would go to the Federal section, click on Wages and Income, and find the W-2 section (Wages and Salaries).
You can preview your Form 1040 entries throughout the process by taking the following steps:
1.) On the left-hand side of your screen, click Tax Tools
2.) Click Tools
3.) On the window that pops up, click View Tax Summary
4.) On the left-hand side of your screen, click Preview My 1040