Werw do the 2wires white , connected to a 5 post,

It depends on what model of thermostat you are wanting to hook up. Your owner manual should show where the wires should be hooked up.

If you are unsure, give us the make and model number of your thermostat so that we can help further.

As RickJ said, make and model of thermostat would help.

Most conventional thermostats have r,w,g,y,c. If you only have two wires coming from the heating unit, usaully one goes to R. and the other goes to W. You may have Rc, and Rh, just hook one to Rh, and if there is a jumper between Rc and Rh, just leave it in, if no jumper, don't worry about it. Let us know a little more about your stat and we will do our best to help.