You plug it into the wall or a thermostat, whichever you're going to use, set it on low and monitor your temps. As David mentioned, it is best to leave space for airflow between the heat pad and container, but it only requires a little, like 1/4"-1/2", which can be done with rubber feet for electronics or furniture for a buck or two. The thing about the reptile heating pads is that they often get very hot -- 130F or more sometimes, have no built-in heat regulation (like Hi-Med-Lo settings on a heat pad), and often heat unevenly. They can cause glass to crack and plastic to warp, not to mention burns on a snake, particularly one that likes to burrow, as many do. It's not like they're evil (like heat rocks), but they are typically beat for features, price, and performance by human heating pads.