Top menu >> Reps 

In most cases the Rep ID is created automatically by importing your commission data. Best practice is to have both the Rep ID value and Account value to be the same, you can set this up in the Import matrix

View the Rep.

On the Rep page find the Rep IDs box and click Assign

The Rep IDs box might be in a different position as you can drag and drop the boxes around and change the layout of your page. 

Click Add rep IDs and assign them.

Add the Rep ID in the area next to the supplier(s) you want to add the Rep ID for. 

Click Finish when done.