I have a few questions for you, first:
How large is the turtle?
How large is the aquarium?
Does your turtle have a basking spot?
Turtles can require more care than people often realize. But once you uderstand the basics, it is pretty easy, and a lot of fun. I will give you a quickl crash course in what your turtle's enviroment should be.
ENCLOSUREYou can use a regular glass aquarium. The size really depends on your tutle. A good size for a full grown Painted turtle would be a 55 gallon. Females grow a bit larger than males, and they may require a bit more space. The tank should be filled with water about five inches from the top. At the surface of the water, you will need a basking spot. I suggest a
Turtle Dock or
Turtle Ramp. This provides the turtle with the necessary space to get out of the water. Above the basking spot you should have a
basking lamp. You can top the tank with a screen lid, and place the lamp on top of that. You should use a sumbersable aquarium heater to maintain water temperature, which should be in the mid to upper 80s.
FOODYou turtle should be fed a nutritous food like Reptomin turtle pellets. Insects are good, bu not as the only source of food.
You may know all of this already, but by your posts it sounds like you are new at this. Make sure you setup is up to par, and let us know how things are going.
Good luck!