I'd recommend contacting the Accounting Seed customer support team to verify if they support the ability to map QuickBooks Online to them. This way they can give further info and provide instructions you need to do.
You may also utilize our QuickBooks Apps store to search for third-party apps that can help you map QBO to Accounting Seed.
Here's a great source where you can find articles that can help you in managing your books in QuickBooks, please visit our Help articles page. This includes topics such as reconciliation, track income, and expenses, run reports, etc.
Should you need anything else, don't hesitate to comment below. I'm always around to help if you have other QuickBooks-related concerns. Stay safe and take care always.