As said above, nice hot basking spot. 45-60 degrees or so. A tile, piece of slate or bluestone paver will work really well, distance from bulb will vary with the wattage. Use trial and error with a thermometer (infrared ones are really useful for this) to get the distance right. Use a 24hr timer for this, not a thermostat.
If you opt for background heat at night then use a thermostat (pulse proportionate preferred over switching thermostat) with the heat source (ceramic heat emitter would probably work best). I don’t have background heat on my monitors because the bluestone basking sites make wonderful heat sinks and radiate it back out when the lights are off, but it will depend on how well or badly your enclosure holds heat.
You want the cool end of your enclosure around the high 20s.
Sticks and branches to taste for climbing and a layer of sand for substrate, plus a couple of hides in different areas. Small bird boxes screwed up high on a wall will do pretty well. Add some dead gum leaves over the top of the substrate if you like, it’ll look nice and your little fellow will forage through them.
I recommend quickly going and buying a book called “A guide to Australian monitors in captivity” by Danny Brown. Has loads of husbandry dos and donts, dietary information and other specifics you will need to know.
