how to do 1040 only?

Prepare only a federal return---you are not required to prepare a state return.

 

A 1040 is the tax return form you prepare here to send to the IRS.   If you start entering data in this software you are preparing a Form 1040.   Please look at it so you will know what you are sending to the IRS:

 

PREVIEW 1040

 

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.

 

 

 

 

If you live in a state with a state income tax, you can look for other ways to prepare your state return--often the state has a website you can use.