First, make sure you have Acumatica 2018R2 or later as well as being logged in with a user linked to the customizer role.
You need to add the additional fields you want to use in the Sales Order screen as attributes in the system. Navigate to “Configuration >> Common Settings >> Attributes” screen CS.20.50.00 and add some attributes. I will add a combo box.
Create a new Sales Order and click on “Customization >> Manage User-Defined Fields”.
Click on “Add User-Defined Field” and add the Attribute you have created earlier. The Column and Row options are used for arranging the newly added User-Defined Field on the screen. Click OK and the back button to the left of the “Add User-Defined Field” button.
When you look at the Sales Order screen, you will now see that the document header have an additional tab called “User-Defined Fields”. This section stores the additional information you require during processing.