Here is the instruction from the manual to set frequency. I had to try a few different ones till I got the best one.
At the Transceiver J-box, remove the cover to expose the PCB. On the PDA Handheld Remote, press
and hold both the UP and DOWN arrows simultaneously for three (3) seconds. After3 seconds, the CHANNEL SETUP screen
appears. Select a channel. On the PDA Handheld Remote display screen, a prompt will appear with instructions to slide the J-box Learn Switch out of LEARN (OFF) and to press the J-box Reset Switch. At the PCB in the Transceiver J-box, slide the Learn Switch out of LEARN and press the Reset Switch. The Red and Green LEDs on the J-box will blink simultaneously.