UHF repeaters

I just got hold of an entry level 5watt UHF handheld for hunting trips, as my usual partner has Garmin rino. Looking into stretching the range of coms using these units it strikes me that the avavilable repeaters in NZ are using a different frequency to our handhelds.
Handhelds are on 476.425>412.412 mhz, and repeaters are on lower mhz.
My unit says in the destruction book that it can utilise repeaters when set to correct channel, but doesnt tell me how to set it to duplex capability. Do most units swith themselves automatically if you have them on a repeater channel ??
Sorry for sounding like a dumbarse

http://www.nzart.org.nz/assets/maps/current/u-ni.pdf