This phrase is used here to mark the beginning of a new part of the story. If your language has a way for doing this, you could consider using it here.
## hand was shriveled ##
The man's hand was damaged in such a way that he could not stretch it. It was probably bent into almost a fist, making it look smaller and wrinkled.
## were watching him closely ##
"were watching Jesus carefully"
## so that they might find ##
This could be translated as "because they wanted to find."
## in the middle of everyone ##
This could be translated as "in front of everyone" (UDB). Jesus wanted the man to stand where everyone there could see him.