I'll be blunt.
Ask yourself this: if you don't know what to do with an animal, why are you taking it in?
First of all, stop accepting turtles from friends who just pick them up. In fact, in my opinion, you should be actively discouraging people from doing this.
While you may have good intentions, I think that you don't have a full understanding of state laws & regulations or the multitude of other issues involved with collecting and releasing box turtles, namely the health risks and site fidelity considerations among other factors.
With this turtle, find out from your friend where he was field herping and return the turtle to that area. If you get your friend to really think about it, I bet he could remember where he found it in the first place. If he can remember what day, he can probably remember what area, and even what stretch of road. If he really does field herp, he'll know where he was.
You are not doing turtles any favors by translocating them. Do some more research. Get informed.