## uncover his feet ##
to remove the cloak or blanket covering his feet so that they would be exposed to the cold.
## Lie down there ##
"lie down at his feet"
## Then he will tell you what to do. ##
The specific custom of that time is unclear, but this is usually understood as culturally acceptable way for a woman to tell a man that she was willing to marry him. Boaz would understand the custom and accept or reject her offer.
## Then he will ##
"When he wakes up, he will"