Freelunge him, then do some basic groundwork, such as leading, you will know when he trusts you, he will easily follow you around, and when something is bothering him, he will look at you with "worried eyes". When he looks at you with the "worried eyes" you need to halt, and comfort him. Many horses find it comforting when you lead your neck against theirs and face the opposite direction, put your left hand around under his chest, and massage both shoulders, just pressing inward gently and moving your fingers in circles and you should be able to feel his muscles start to relax and he should start to drop his head and relax, then you can move on with leading. Lead him EVERYWHERE but work with him slowly and patiently, introduce new areas slowly, let him take a break and take in a good long look at the new area then relax him. He will learn to trust you and believe when you are calm he is calm.