Did you get a thermostat with that under tank heater? If not I wouldn't put any animal in there until you do. You NEED a thermostat for any heat source just to be safe and also to control the environment.
Water dish can be placed anywhere, so long as you change it when it's soiled/stale/evaporated.
I would recommend something other than carpet for bedding. Not good for humidity or cleanliness(unless you want to go through the hassle of washing it everytime it's soiled). It's easier to use disposable bedding such as newspaper, papertowel, or loose substrate.