My boyfriend has trust issues because he was cheated on in the past how can I get him to trust me?

If he is paranoid ? Difficult , therefore my advise is before starting a relationship is to be open about u past , and expectation . Try to see if he is willing to consider family therapy.
You can't. Trust is not something we can demand of others or even ask for. What we can do is show ourselves to be trustworthy. It is up to him to decide to trust or not. Be careful not to make yourself a prisoner of jealousy by trying to prove you are trustworthy. You can go overboard insisting you can be trusted till you lose your freedom and individuality. That may lead to more distrust and unhappiness.