how to add Debt card to existing bank account

Thanks for dropping your concerns here in the Community space, @Lisa 85. Let me help you manage linking your debit card in QuickBooks Online (QBO).

Beforehand, are you trying to set up the debit card as a subaccount to your existing bank account? If so, there's no debit card account type when setting up a sub-account. However, you can set it up as a bank account. Here's how:

1. Go to Transactions and click Chart of Accounts.
2. Select the New button. Choose Bank as an account type, then fill in the following fields.
3. After that, tick the Is sub-account box, then decide on a parent account.
4. Once done, hit Save and Close. 

On the other hand, if you're referring to something else, feel free to add more details. We want to provide the resolution you need regarding your goal. 

You may also visit this article as your guide to handling special accounts inside QBO: Manage default and special accounts in your QuickBooks Online chart of accounts. 

Reply to this post for more questions about adding a subaccount to an existing account in QBO. I'm here to assist you. Have a good one!