To link your husband's two Capital One accounts to QuickBooks Online, you can follow the same steps you used to link your accounts. Here are the general steps to connect a bank or credit card account to QuickBooks Online:
Go to Transactions, then select Banktransactions.
Select Link Account.
Enter the URL or name of your bank in the Search field, then select the bank.
Enter your Sign info in the Login and Password fields, then select Continue.
Select the account that you want to connect and date to pull transactions from the dropdown. Then, select Next.
Select your account type on the Account type dropdown, then select Next.
If you don't see the correct account type, select +Add new.
I'm adding these articles as your reference in connecting and steps to set up your bank and credit card account in QBO: