Big dogs outside have big barks. Your large dog may enjoy being outside. But he also may intimidate the neighbors, small children around the neighborhood, or smaller dogs next door. If staying in your backyard or running free might be more appealing to your dog then lying around your living room, training him to be an inside dog might take some time. But once your big guy is used to being in the house, he'll find comfort there as well. If you're living in an apartment or a townhouse with close neighbors, you need to be able to teach your dog to be inside without being miserable enough to bark all day there as well. This is a simple training, giving him safe spaces where he can find comfort just as he does when he's outside. Your large breed dog may also be very protective of your space and the people in your home.
Some dogs believe they can protect better from the outside. Teaching him that his role is to be inside will also help him want to be inside the house. To give him this control for protecting your house, you can start by giving him small areas in the house to protect or to call his own. Doing this will ease him into wanting to be in the space you have assigned to him. You can do this by keeping him on a leash in the house so he has the feeling of being outside. At first, if you are using a leash for indoor training, you may need to take the big dog outside when he sees the leash because he may be used to being out on a leash. Make this a quick trip outside, and when you get back in just don't take the leash off of him. Leave it on so he feels like he's still on duty when he's in the house and has the power to do his job. Another thing you will need to focus on is creating this space that is his. His space should have his belongings, his comforts, and give him a reason to want to be indoors instead of outside.
To convince your dog to be inside all the time you're going to need a leash, lots of lovey toys, a comfortable bed, and some treats. If you give your dog treats inside of some fun toys, he can associate playtime with inside as well. If your dog wants to be out to watch the world revolve around him and protect the center of his universe then assign him to a special room where you keep his belongings and where are you with your family.