HSA distributions are reported on form 1099-SA which is sent to you by the HSA custodian.
To enter it, please do a Search (upper right) for "hsa" (lower case and without the double quotes), and jump to it.
After you check off that you have an HSA, almost the first screen is asking if you spent any money out of the HSA. Answer "yes", and enter your 1099-SA information in the subsequent screens.
