I appreciate you taking time to contact the Community. I'd be delighted to help you connect with BMO Harris Bank in QuickBooks Online.
There are just a few steps in the process. Here's how you'll get started:
1. Click the Banking tab from the left navigation bar.
2. Select the green Add account button in the top right corner of the screen.
3. Enter BMO Harris [Bank] in the search bar.
4. Choose the correct institution from the list.
5. Enter your credentials and click Continue.
This article will walk you through the rest of the setup: https://quickbooks.intuit.com/community/Banking-and-bank-feeds/How-to-add-and-connect-bank-and-credi....
Once your bank is connected, you may want to check out this write-up, which provides details on categorizing, editing, and adding downloaded transactions: https://quickbooks.intuit.com/community/Banking-and-bank-feeds/Assign-categorize-edit-and-add-your-d....
Feel free to comment below if you have other questions about bank connections or anything else in QBO. Take care.