Hi info383,
Your accountant must use their own QuickBooks Online for Accountant password to be able to sign in to their account. Once done, your company will be added to their client list.
Please have your accountant follow the steps in this article: How to add a client to QuickBooks Online Accountant.
If they don't have a QBOA account, they'll need to sign up so they can access your account.
Keep us posted if you've got more questions.