You can find information on how to take care of your land turtle from websites like turtlepuddle.org/american/boxcare.html and www.wikihow.com/Take-Care-of-a-Land-Turtle. Land turtles aren't expensive to keep considering they eat most types of vegetation and don't get sick often.
It also may have been illegal to collect it. Many box turtles are protected species. Just be sure you know what you have. Diets vary quiet a bit by species and since these turtles can live for 50+ years you want to feed it correctly. Be sure you can commit to the task too. I had one for 27 years!