Let him get used to you.
If he wants to hide, let him.
He'll come out if he wants to eat.
Talk to him in a soothing tone of voice.
Think of it from his perspective - you are way larger than he is, he's in a strange place, and may have previously been abused.
I follow a person on Twitter who had this same experience with a cat. Lesson he learned - let the cat decide what's comfortable for him.
Scroll back to his posts from last winter (October/November 2018). You can do that without signing up for Twitter. He adopted a shy, frightened stray who wouldn't come out from behind a chair. Months later, the cat was sitting on the couch with Josh, watching TV