If you enter Terminal E on the departure level, go down one floor to arrivals. As you face the exit area from immigration and customs, on the right is a single door -- almost in the corner -- that may or may not have a Global Entry sign next to it. I believe it is at least marked with the Customs and Border Protection logo. Through that door is a small hallway; at the end of that hall is the office where they conduct interviews and such for Global Entry.