The option of adding a Health Saving Account is available in the Financial Assets area for each adult if married or partnered. If you do not see it, you can "restore" it from the dismissed items group in the middle of the page after selecting "Financial Assets."
You can add a description, the current balance if any, and the contributions and withdrawals. Contributions are assumed to be pre-tax and qualified withdrawals are not taxed and appear as withdrawals in the HSA report and as spending in the Spending report in the Other column. Unqualified withdrawals will show withdrawals in the HSA report but not show up in Spending > Other but instead will go into regular assets.
The report for this account will appear under Financial Assets for each adult.