If I did not receive a 1099-SA but I would like to input contributions from my 5498-SA, how can I access a screen for that?

Contributions to an HSA are independent of distributions - you can certainly have some of one and none of the other in any given tax year.

We normally tell taxpayers that they are not required to enter data from the 5498-SA into TurboTax. By that we mean that we assume that you know the sum of direct contributions that you made through the year so don't need to refer to the 5498-SA.

It absolutely WILL MAKE A DIFFERENCE to enter your contributions. Direct contributions (that is sent straight to the HSA custodian not through your employer) are added up and put on line 13 in Schedule 1 (1040), which reduces your taxable income(!).

If, however, you made contributions through your employer, then you will see an amount with code W in box 12 on your W-2. This has already been taken out of your Wages in boxes 1, 3, and 5, so you have to go through the HSA interview and show that you had the proper HDHP coverage. In this case as well you need to enter your contributions (although in this case, you already have when you entered your W-2).

So, tell TurboTax that you have an HSA and in the HSA interview, enter any direct contributions that you have made. (DO NOT enter your payroll deductions again, because they were already entered as part of the code W amount).