Start with the basics - put the H8 into GMRS mode, ensure the standard 22 GMRS channels are programmed in (menu #35 on my H3 is where "Reset -> Channels" is located on the device, if you want to try a reset - it worked for me in the past, but ODMaster works too). Ensure you're using the longer whip GMRS antenna ("771") on the H8 instead of the stubby one. (NOTE: HAM and GMRS antenna have different attenuation - check the writing on the antenna base you got for xMas). You can buy these on Amazon for $10 if needed.
Create an account on this other site and find something close to you (there are 46 listed for AZ, many around the Phoenix area - typical repeater can cover 20 miles? depends)
https://mygmrs.com/repeaters - listen in on your local repeater channels and you should hear some chatter. A handheld doesn't have great range so you're really wanting to leverage your local repeaters to communicate. Do not talk (broadcast) until you get a license.... ->
PSA: GMRS and HAM require a license from the FCC. with the GMRS license being simple - pay some money, get a GMRS callsign good for 10 years. HAM requires a lot more (tests, money, studying) hence my suggestion starting with GMRS to learn and you can broadcast once you get a license for it. GMRS range is very limited though at 5W so you needa good antenna and those repeaters in your life.