Introduce one room at a time and let him explore and see what he does. Make sure there's nothing around that he can get choked on, and nothing poisonous, like ant traps or something like that. Also, be careful of any wiring. When you first let him start exploring, make sure to tell him no if he tries to chew on something. He will learn. It's pretty much like baby proofing the house. Also, make sure he can't get to any wastebaskets or toilet paper. They love to take the end of the roll and run with it.
In the beginning, I kept mine on a leash in the house. That way, they got used to the leash, and I could keep an eye on them until they got a little bigger.
If you're not home, it's better to keep him crated or confined to one room where there's nothing he can get into. I gated mine in the kitchen, but now they both have free run of the house, and they never bother anything.
Good luck!