Click on the Federal Taxes tab, then Wages & Income, then scroll down to Less Common Income and select the first item in the list, 1099-SA, HSA, MSA. On the next screen, you'll select Health Savings Account (HSA) from the list of possibilities.
Hit "Continue" and you'll land on the summary screen that says Here's What We Have So Far, which will show any 1099-SA forms already entered. You'll also see a button for Add Another 1099-SA. Click on that, and follow the prompts to enter another 1099-SA form (you can repeat this process as many times as you need to enter multiple HSA forms).