It's fantastic to see that you're using QuickBooks Online for your business needs. One of the great things about this program is how you can individualize it to your organization. I can guide you down the right path.
It sounds like you're referring to categorizing transactions in your bank feed. When you enter a transaction through your bank feed QuickBooks remembers the category you used and will present that as an option for similar transactions in the future. You can create rules for transactions if they're ones that you use often. I'm providing a video tutorial and an article that goes through the processes in detail:
In the case that you mean that your invoices are ending up in the wrong sales account or product category, I'm also providing articles that explain how to manage the account and category through your products and services: