This should help:
https://www.youtube.com/watch?v=tfmt7C8j3MgI'll also add this for those who may be interested. There is a shower outside of security at the Sheraton, which is upstairs from arrival and down some hallway a bit. It's 5 euros more than Mercure or Yotel, but if you're going to be staying a bit longer or otherwise pick up your luggage, then the Sheraton is a good option. Essentially, you buy a day pass to their spa. My flight often arrives early in the morning and I can't get into a hotel room until 14:00 or 15:00. I have to pick up my bags, so if I'm going to clean up, I either need to shower
very quickly at one of the showers inside security before my bag gets to the belt, or else pick up my bag first and use the Sheraton, located outside of security.
http://www.sheratonamsterdamairporthotel.com/daypass