The sales order header now has a tab. The following path will get you there:

Sales Order with Commissions tab
In addition, the Sales Order Line Item screen also has a tab. Following this path will get you there:
Enter a customer in the text box next to Customer #:
Select the tab.
Click .
Enter an item in the text box next to Item Number:
Enter a quantity in the text box next to Qty. Ordered:

Sales Order Line Item with Commissions tab