I have a 1750 watt stelpro baseboard heater and I want to hook up a stelpro n2t1w double pole themostat. Could you give me the correct wiring diagram? I have 12-2 wiring power in.

Your 240v power supply will connect to the black wires, and the red wires connect to the heater. The white wire should be marked with tape to indicate it is a hot wire, not a neutral, at both ends, in the panel and at the heater. There is no neutral with a 240v heater.