For now, place the lamp over the log.

They need a warm side and a cool side. The warm side should be between 88-94. You need to get a thermometer with a probe. Go to Walmart or Home Depot in the garden section, Accurite is a good brand, make sure it has a probe.

There should be a hide in the cool side and one in the warm side.

I recommend getting rid of the lamp and getting a UTH (Under the tank heater) and a thermostat.