To add your W-2s, follow the steps below:
Log in and click Take me to my return
Click Federal Taxes and then Wages & Income (If you have the blue button 'Check for more income', click it and then click 'Skip to see all income')
Next scroll down to Wages & Salaries and click Show more
Click Start next Wages & Salaries
Next, you'll be able to add your W-2. When you come back to this section after, you'll be on a summary screen of all W-2s entered. Click "Add another W-2" to add another form.