Stop the next steps will differ depending on which thermostat you are installing for single pole thermostats.
How to install a double pole wall mount thermostat.
While this type of installation is easiest since it does not involve opening up walls it is considered to be inferior to installing the thermostat on the wall.
Using a wire connector connect the hot supply wire to the thermostat wires.
Then remove the thermostat from the wall.
Typically this is marked l1 or line step 8.
In my experience the wall mounted unit will control the temperature if placed in the appropriate location.
Thomas with cadet tech support shows you how to install a double pole wall thermostat on a 240 volt electric baseboard heater.
Make sure to connect the ground to the thermostat or wiring box if available.
For one thermostats situated in the lower 6 inches of a room are not accurately measuring temperature since cold air sinks.
Since you are working with a double pole thermostat there should be four wires.
Double pole 22 amp 120 volt 240 volt wall mount mechanical non programmable thermostat in white designed to replace most wall mounted line voltage thermostats 4 wire thermostat with color coded wires for easy installation.
Two of these are live wires and two are load wires.