WRWA967

I am new to GMRS and the 4X4 group I'm mentioned using custom channels. I have a BTECH GMRS-Pro and either miss understand or do not know how to program a customer GMRS channel between 462 and 467 Meg. I help either explaining custom channels since I can program the RX, but not the TX. Or helping me program my radio. Thank you in advance.

Continuing on the GMRS Pro topic. Seems like a good radio, but the antenna is not so hot. Been trying to find the specs on the antenna it came with, but to no avail. Can anyone suggest an upgrade antenna?