How do I install a programmable thermostat?

I only have one white wire and one black wire. I am assuming the white goes with the white but i dont know what to do with the black.I have tried a couple different combinations and every time i turn the power back on the furnace kicks in at 100%....even when i have the thermostat set to off.How do I install a programmable thermostat?read the instructions that came with it