If you meant to associate the sales invoice amount to a revenue or income account, then you can set it up on the Product/service information window.
Here's how to associate your item with a sales account:
Go to Sales.
Select Products Services.
Click New.
Under Product/Service Information, select the appropriate type of your item.
Enter the name on your new item.
On the Income Account menu, select your sales account.
Click Save and close.
Once done, you can add the item under the PRODUCT/SERVICE column when creating an invoice for your sales. Doing so will post the invoice amount to a revenue or income account,