You will probably need to create some accounts for mapping to your ecommerce or point of sale system.
Often it is good practice to use new account if you are switching from another method of posting sales to QuickBooks online.
First login to QuickBooks online
Then on the left side go to Accounting
Choose Chart of Account
Then Create the Account. See below for some common types of accounts you will need to have.
Expected Payments Account
In ecommerce and retail you will receive payments from many different channels. Most often you will have a credit card processor and cash. But sometimes you may get payments from special payment processors like Paypal or Shopify Payments. Each of these payment vendors deposit money into your bank account at a later date.
So you need to keep track of how much they owe you.
The best way to do that is with an account with a Name of "Expected Payments Shopify Payments" or "Expected Payments Paypal" etc. The Account Type is Other Current Asset the Detail Type is Other Current Asset and the rest you can leave blank.
Cash Payments Account
Cash payments into the register can be tracked in several ways. The simplest way is to create a Bank type account called "Cash On Hand". Then when you deposit money into your Bank type account for your checking account you will do a transfer from "Cash on Hand" to "My Checking Account. Also, this allows you to use the "Cash on Hand" account for petty cash.