You can use money in your Health Wallet to pay for qualified medical expenses, as the IRS defines in Publication 502. The full list is available here: https://www.irs.gov/pub/irs-pdf/p502.pdf
Please note that some expenses, like gym memberships or vitamins, are only reimbursable if you obtain a doctor's note.
Have a question about a specific expense? Email firstname.lastname@example.org for additional help.