The basic answer is you go to the airline operating your first flight and they will give you at least your first boarding pass and probably the next two as well. If they don't/can't/won't, you can usually obtain your boarding pass at the gate (or transfer desk if it exists) at your connecting airport. There's no need to exit the secure area unless you have to change terminals or recheck bags.

Note that NWR is not a valid airport code. Possibly you meant EWR.