monitors can be lazy lizards but since you got a juvenile it's best to have lots of space for it to move around. provide a large water bowl as they love dipping themselves in and excrete waste in the process as well.
i have an 18-inch juvenile asian water monitor that i keep in a 14-inch clear plastic shoebox. i let him dive in a bucket of water every morning after sun basking. after defecating, i just let her loose around our apartment for a few hours