Don't worry, it's explained thoroughly before you start the assessment. :-)
If you head over to this page, you'll find a video showing you the various bits of COMPASS.
http://www.epst.com/com/compas.html
If you skip through, you'll find the orientation one. The RBI points towards the big cross in the middle of the screen, and hopefully the compass and AI are self explanatory. The green arrow shows whether the plane is climbing or descending.
You have to work out which little airplane corresponds to the scenario shown in the instruments. In the example they have on their website, it's number (1).
It's descending, flying directly away from the beacon, and heading west.