Most Helpful Guy
This really depends on what broke the trust. Cheating? Lying?
But, in the general sense, for someone to trust you again, they have to want to trust you again. Meaning, they have to want to be with you again. This is part one.
Part two is time, attention and letting them release. You have to understand it will be hard for them to trust and you must let them release. It will take time and getting your attention will matter because they'll see your commitment.
The rest is hard to really answer without knowing why they don't trust you.