I need to fill our 1040SR for my dad. When I search for the form using Intuit Assist, it takes me to add/edit schedule C. How can I get to 1040SR?

The Form 1040-SR is exactly the same as the Form 1040, it is the federal tax return that is filed with the IRS.  All of the income, expenses, deductions, credit that are being entered in the Federal section of the TurboTax program will be on the federal tax return Form 1040/1040-SR.

Form 1040-SR will automatically print for taxpayers 65 or older when using TurboTax Online.  If you are using TurboTax Desktop, it'll give you the option to print the 1040-SR. It contains the same information that the 1040 contains, but the print is larger.

Refer to the TurboTax articles Everything to Know About the 1040-SR Form for Filing Seniors for more information.  If you would like to see a copy of the form, here's the link Form 1040-SR.