If you are talking about an HSA contribution directly to the HSA plan administrator outside of your employer, you do the following:
- Go to Federal Taxes->Deductions & Credits->Medical and click on "HSA MSA Contributions".
- If you see the HSA Summary, click on Edit to restart the HSA interview.
- Proceed through the HSA interview until you come to a screen entitled "Let's enter [your name] HSA contributions" (see screenshot below).
- Enter the additional personal contribution on the second line.
