ARC500 - Programming a Custom Fleetmap?

[wnjl]

I’m attempting to program in the NJ Transit TRS on the ARC500 software, it uses a hybrid Motorola system. When attempting to put in the custom fleetmap in, I select the “custom” option in the dropdown window under Fleetmap for the NJ Transit TRS, but I see nowhere to enter in the custom system map (double clicking on custom just gives me the dropdown window I already selected from). I assume there must be a way to do this in the software, does anyone know how?