Be nice to people and say hi. Don't lose confidence, remember you got this. Also take good care of your horse and if you want you can even ask to help around.
Be polite and say hi to people when you first walk in the barn. Follow all the rules. Be confident in what you do and how you care for your horse.
Keep track of your horses health. New barn= new hay and a lot of horse have different reactions when their hay is switched.
be confident first step in but at the same time be polite and everything else will come to you slowly