The thermostat hookup is 2-wire and there are 3 screw connectors inside the thermostat. I need to know how to connect the wires.

How are the wires labeled? Take an ohm meter and find the two connections that open and close when the thermostat is moved from low to high and vice versa. The two connections that do this are the ones you want. If the screws are labeled "R," "W1," and "W2" then use "R" and "W1." "R" could also be labeled "C" or common, but that would be rare.