I'm replacing my old thermostat with a new hunter programmable one and the old sears thermostat that I have only has two unmarked wires. How do I tell what the wires are for and will it work with my new thermostat

1st ,I need to tell you That hunter tstat is junk, if it works at all a year is about all its worth
With that said are you saying you only have 2 wires to work with? If this is right this means you just have heat only,no ac., If all this is correct,tie one wire to R or rh,, and the other wire to W posts

Before you do all this kill the breaker to furnace,we don`t want any sparks