You go in and you are all briefed. You obtain your spy identity and familiarize yourself with your cover story. You proceed into another room and are tested to see if your cover holds up or you have alerted others to the fact that you are a spy.
There are many actual spy artifacts from old time to the most up-to-date. You can test your skill in breaking codes or sitting at a computer finding missiles and planes that are hidden. You can listen to earphones picking up soundwaves and other people's conversations going on in the building. Many old spy TV shows are displayed, which is fun for the nostalgic, like "Get Smart" and "Man from U.N.C.L.E." There is a room dedicated to female spies like Mata Hare and Belle Boyd from Civil War fame.
It was a wonderful museum, but, like most DC museums, it is hard to take it all in in one visit.