If you are in the TurboTax online version, you are not able to switch over to Forms Mode to input/remove things on the forms. You will need the CD/Download version to get directly to the forms.
If there is a specific section you need to edit in online version, you can input that form name in Search box in top right, and jump to that section from there. Or go to My Account, Tools, Topic Search and type in what you are looking for.
NOTE: If you have not filed yet and you need to view just your 1040, you can do that by clicking My Account in top right, choose Tools and then View Tax Summary. Once there, click Preview my 1040 near top.
https://ttlc.intuit.com/replies/4225653