The probe from the tstat goes on the OUTSIDE of the tank. It goes between the glass and the UTH. Your tstat needs to be set on whatever temp that is needed to achieve the 90 hot spot on TOP of the substrate(probably around 93-95). You should only have about 1/2"-3/4" deep substrate. Any more than that makes it hard for the heat to get through. Make sure you are measuring the temperature on the TOP of the substrate with the accurite unit or the probe because that's where the animal will be. As for the lamp you will need a 50-75 watt red or blue night time bulb in a ceramic fixture. It needs to be left on 24/7 to keep your ambient air temp around 80. Also it helps to cover the screen mesh completely except for where the heat lamp will sit. This will help to hold heat and humidity. Here's an example, it's covered with insulated bubble wrap. Most people use plexiglass or damp towels. Here's my 10 gallon.