How in Metal Gear Solid peace walker do you ap scan

Its quite easy. And sorry if you already know this...

In the top right there is a button that resembles sound waves. It should say recruit. If you don't have this icon you need to advance in the storyline.

Press X on it. You will see a flashing red icon with an arrow on it. Select it by pressing X and a pulsating circle will flash twice. As this happens repeatedly press the O button. If you are standing in a good location and have pressed the circle button you will hear a confirmation sound and see " MSF EXAM" Press the X button and you will be taken to a mission on a rainy beach. The number of soldiers will vary. The most I've had was six. you need to take these soldiers down with hand-to-hand or CQC (basically the same thing). Once they have been successfully knocked out you will be taken back the the RECRUIT screen. Go back the mother base and you will see that the soldiers that you knocked out have joined the MSF. Their skills are better than most found in game.

Also, only one EXAM can be taken in the area you are standing. If you see this message,

Unable to locate access point.

There do not appear to be any volunteers nearby.
Please try again somewhere else.

just listen to it. Move around. You are bound to find some Volunteers somewhere.

Hope this helps.