I'm happy to see you're looking to get all your sales into QuickBooks Online! Being able to access an extensive history of your financials is an area where the cloud-based nature of the program really shines. The more transactions you bring into the system, the more you can learn from your reports. I'll be happy to help you bring these in.
The two easiest ways to bring in transactions manually are through the invoice import option, and the bank feed. The invoice import process allows you to easily import a large number of unpaid invoices. This is particularly useful if you're interested in simultaneously bringing in your customer and products lists as well. To learn more about this, check out this great guide: Import multiple invoices at once
The bank feed options is best for importing a large number of sales, without being limited to just open invoices. If all your sales get deposited in the same bank account, this is the quickest way to bring them all in. It's just a few easy steps to get started: