I am replacing my old manual thermostat with a new programmable honeywell 2300. My old one only has a white and red wire. Were would I connect the wires? I just have a gas furnace, no AC.

You only need 2 wires for heat. The new T'stat should have an R and a W terminal. Connect your wires to them. Didn't it come with instuctions?

This is a HVAC question and should not be in exterior home improvement. Try this to help you understand the wires https://www.askmehelpdesk.com/heating-air-conditioning/heating-cooling-maintenance-repair-troubleshooting-faq-northerheat-58313.html