If you already stuck the UTH to the tank you will need to peel it off and place the probe from the thermostat on the center of the UTH. So basically its in this order... UTH / Probe / Glass. If your UTH wont stick right get some Foil tape and tape the UTH back to the glass tank. Don't tape the whole UTH just tape along the sides of it. After that set the thermostat to lets say 92 degrees. Place your thermometer probe in the substrate under the hide and place the unit itself on the opposite side of the tank. Give it some time and check the thermometer and see what the temps are. If it's to high or to low adjust the thermostat accordingly. The more bedding you have in your tank the higher you are going to have to set your thermostat.