Use the arrows or channel knob to select the appropriate "Rept" channel that corresponds to the frequency you want to use.
Hit "menu" and scroll to t-ctcs or t-dcs as appropriate (if the tones have a decimal, most likely ctcss...if it's 3 digits only, sometimes followed by N or I, that's dcs).
Hit menu on the appropriate option, them scroll through to the appropriate tone number from the repeater listing or other info source.
Hit menu to confirm the code, and then exit.
You should now be good to go. You can get into things like adding custom channels or names via computer (and programming cable) but this will have you up and running; from there it's just "am I in range? And "is anyone listening?"