Just be consistent when working with him and fair when correcting him. With a new horse I expect good behavior but it doesn't initially have to be perfect
Textan is right consistent and fair
Let go of the NEED for trust right now. It will come on its own. When you make a new friend can they "make" you trust them? Can you make then trust you? How does that trust grow? What causes a person to not trust other people? The same goes for horse.
I don't worry much about trust when working with a new horse...really I don't worry much about trust ever now that I think about it. Trust come through be consistent
the more consistent you are the more you horse will trust
that they know what you want from them and where they stand in your little herd of two. If you are not consistent with rewards and with punishment your horse will not trust
you because they will not know what is expected of them in any given moment.
Put you self in your horses place do you like people that are consistent and fair? Do you like clear defined boundaries with clear and fair consequences? Your horse is the same way in a herd they want and need boundaries they what to know how is the boss.
I have a herd of 30 horses some of them have been here for more the 10 years. They know how the boss horses are and where each horse fits in the pecking order. When I buy a new horse and there is stress in the herd there is fighting up and down the pecking order until each horse knows it place in the new herd. Some times that take a week or months and once it took almost a year.
The trust will come once your horse know you and understand that you are the boss and that you are consistent and fair. Read all you can about herd behavior don't expect your horse to act like a human it's a horse it looks at you as a two legged horse it understand you when you respond as a horse would respond, when you act like a human that is foreign to your horse.
So get help, read, learn, study to know how you horse sees the world.
Be consistent and fair. Set rules and hold you horse to those rule.
Good luck enjoy your time with your horse