So you've had him for four days? Right now he is trying to figure out where he fits in the family. First, imagine how you see him as an adult. You probably don't want him jumping on you or counter surfing. The first thing you can teach him is a proper sit near the door he will be going out of for potty. The spot should be out of the way of the swing of the door, but so he can look outside when the door is open. If there are more people in the house besides you, mark the spot with masking tape so everyone will be on board. Bring him to the spot and lure him into a sit using treats. Praise and treat and pet for each sit, no matter how long it takes him to sit his butt down. Once you have him plopping into a sit when you move your finger or hand over his head, repeat twenty times. You can lure him into the sit, then pat your leg and say, "let's go" to get him up again, walk in a circle and have him sit in the proper spot again. And again. And again. Have him sit in the spot every time you will take him outside, praising and treating him.
Outside and on a leash, bring him to the place you want him to poop in. Walk him back and forth until he does his business. Have a treat ready. The instant he is done, give him a treat. Give him a treat for peeing, but only the big pee, not every little marking. Once you've completed the treat ritual, pat your leg and tell him, "let's go", walking away. He should follow you. If he doesn't, don't drag him, cajole him until he follows you. You want him to learn that "let's go", or the leg pat means, "I'm going this way and so are you."
Once he's learned sit, have him sit and wait for his meals, sit by the door, sit for any and all treats or toys. If he is a jumper. have him sit when he comes up to you instead of jumping. It will become a default behavior which will park him with all four feet on the floor. When you give him an extra snack or a toy, say, "Rover, take", so that he'll associate the word, take, with taking. This behavior can work itself into the retrieve when you want to teach fetch. It will also get him to discipline himself and wait to take something rather than grabbing.
I would also get some raw bones for him to chew on. The chewing will give him something to do with his anxiety at being in a new environment. Make sure the bones are sized to the dog so he can't swallow them, but are small enough he can pick up and carry. Throw out after three days as they become brittle. Bones can be kept in the freezer until you need them. My dogs enjoy theirs outside.
In another post you asked about clicker training. Once you charge up the clicker, you can use it for the sit. Just pay attention so you get the click right, click, treat and praise. When you do advanced work with him you will love the clicker.