I am installing a new honeywell progammable thermo. To my elec. Forced air furn. The problem is that there are only two wires connected to old thermo. A red and a white. These were not coded. I am uncertain to where they connect on new product.

Tx

If its heat only RH and W.

Tx t-top for wiring info. I did that and now I do not think that the fan comes on... is there another wire to connect,, there are a few more wires that are not used. (different colours etc)
Tx
Gord

I wired the thermostat as suggested with only two wires, red, white. To the terminals rh and w.
Should my forced air fan also come on or is there another wire to connect.
Thermostat is honeywell model rth2520 --heat only. There are more colored wires unused.
Tx gord and to t-top for answer to first??