Select "Connect Fiat"
Notice the Transfer and Card Payments, both of these need to have checkmarks not X's to work.
Go though all the forms, make sure you know if you are an "Individual" or a "Business". Once completed, it will redirect you back to the Mintbase site, and then back to your profile. Do not touch anything on the first redirect.
It takes time for Stripe to process pieces of information, so if the button in your profile still says "More Verification Required" you might need to click back into the portal and add more documents.
Once you see two checkmarks you are ready to go and below you'll see all of your stores (smart contracts). Find the store you want to enable fiat for and press "Enable Fiat" and confirm the transaction on your wallet. Once enabled we require all users to enter an email to purchase an item even for ETH only transactions.
Only items listed more than $20 USD will have the Credit/debit card enabled. The things listed for less than will still show, but only have the Buy with ETH option.
See an example here: