How can I attach a bank account that is not linked to a mobile app?

Thanks for your post today, @sarah-silvester2. 

We can connect a bank account to QuickBooks using the mobile app.

Here's how:

1. From the main menu, select Banking.
2. Select + to add an account.
3. Search for your bank. Or choose from the list of popular banks.
4. Select your bank from the search results, then click Sign in to your bank.
5. Follow the steps to select an account to connect to. Or select a QuickBooks account the bank account should map to.

For future reference, you can use these articles for more details in handling bank accounts in QuickBooks: 

• Categorise and match online bank transactions in QuickBooks Online
• Connect your bank feed using Open Banking.

Please let me know in your reply if you have additional concerns. I'll be around to help.