I'm knew to owning BP's as well, but I can give you the advice that many have been giving me. Leave your BP alone for at least a week that includes no feeding. It most likely is not eating because its stressed and adjusting to a new enviroment. As far as feeding the rule of thumb is one rodent the same girth or slightly larger then the thickest part of your snake once a week.

Try taking some sheets of newspaper, and ball it up, and put it in the cage.I've been told it makes the snake feel more secure, and more likely to eat.

Make sure when it does eat, not to hold it for 48 hours after it's meal.

Hope this helps