Hopefully your friendship lasts as long as your boxxie does.
I would recommend a potting or top soil that does not have the foam balls (generally perlite). I'm pretty sure they're just there to help retain moisture for plant roots, but I'm not sure how turtle-safe it is. To be on the safe side I'd stick to the peat moss and plain potting soil.
For lighting, Exo-Terra (?) has a lamp stand you can find in various locations that will position your lamp over the cage. Make sure your bulb/s emit UVB
and heat.
Is your turtle in an aquarium with glass walls? If so, put construction paper along the outside of the glass so that the turtle cannot see outside. If he can see out, he won't notice the glass and will try persistently to walk right out.
Check out
http://www.austinsturtlepage.com for very good care sheets. If you know the type of turtle you have it will speed up your process very much. If you don't then post a picture of him and someone here will be able to identify him for you.
Good luck!