How to file form 1040

Just by answering all the questions and entering all your income etc.  Turbo Tax fill out the 1040 or 1040SR  for you.  Then you continue on through the File tab and either efile or print and mail your return.  You don't pick the 1040 or 1040SR. Turbo Tax gives you the 1040SR if you or your spouse is 65 or older.

Form 1040  -- or 1040SR-- are the forms your tax return is filed on.  it is the form that goes to the IRS when you enter information into this software program.   Please look at it so you will know what a tax return is:

https://ttlc.intuit.com/questions/1901539-how-do-i-preview-my-turbotax-online-return-before-filing

Click on Tax Tools on the left side of the screen. Click on Tools. Click on View Tax Summary. Click on Preview my 1040 on the left side of the screen.