There are many different species of box turtles. They're called box turtles because they have a hinge, and they're able to actually completely retract and close up into their shell by using the hinge on their lower shell, or their plastron. We have several species of box turtles here in North America.
We don't really find them too often in the pet trade anymore, because they're protected by state laws. The clients that I have with box turtles have had them for a very long time before some of those regulations were in place.
The box turtles we have in North America do require a higher protein content in their diet, so in addition to your leafy green vegetables, you're also going to be feeding some protein sources, such as insects.
They require a basking area and the typical setup with heat and ultraviolet light. There are also some species of Asian box turtles that are becoming more popular in the pet trade here in the U. S.
It's very important that you figure out what type of Asian box turtle you have, because some of them actually come from aquatic environments. So you'd be setting up an aquatic type of enclosure instead of the typical land enclosure that we would expect for a North American box turtle.