If you're trying to make sure your partner can't see a specific account, see the article "I need to change what my partner can see".
If you need to completely remove an account from Honeyfi, just head to Settings > Accounts. From there, choose the specific bank. At the bottom of the accounts, you'll see "Delete All Accounts for Institution".
You can always add an account back if you change your mind, but be aware that you may lose transactions older than 90 days.