Hi!
Some say it's bad to have an idea on what the tests cover, since it would allow us to "practice", gain confidence, or stress even more, and ultimately have a bad result in the end. That's definitely true, and I truly recommend you to stay blind on the tests's contents. But this is the Internet (free information), and after all it's up to you if you want to know what the Multipass is. I'll describe it, then. Proceed at your own risk. You don't need any of this to pass the test.
The multipass is kind of an ATC "approach" game. The screen is divided in some areas:
1. The radar: Represents an airport with two main lanes, both ending in a final runway ("Final North" or FN and "Final South" or FS). The north lane has two entry points: A and B, and the final runway (FN). The same happens at FS (D->C->FS). You have also some secondary lanes that, for example, allow planes to change lanes (entering at D but move north, to B, and land at FN). Each plane is represented the pretty much the same way as in the DART.
2. The clock: Everything depends on the clock. It counts the session's time, and everything you have to do depends on it.
3. The strips: You're given a strip for each plane, containing the flight's number, flight level (10, 20, 30 or 40), the route and the timings: it tells you when the plane will arrive at a certain point (for example it enters the radar at A at 0min 30sec, passes B at 3min 0sec, and reaches FN at 5min). You can change the route of the plane if it hasn't yet reached that point (in the previous example, if the clock marks 4min the plane has already passed the B point so you can't change this point).
4. The bay areas: You have some bay areas where the strips fit. One for each point (A, B, FN at the top, and D, C, FS at the bottom). As a plane proceeds from, for example, A>C>FS (thus using the secondary lane, since the main lane is A->B>FN), you have to sort the plane according to its next point. If the plane passes point A at 0min 30sec, and the clock marks 0min 46sec, the strip should be moved to point C.
5. Objective: You have to keep the screen organized, and avoid conflicts (for example if two planes are supposed to land at FN both at 2min 30sec, you have to change the route of one of them in order to avoid conflicts). You can, nevertheless, have both planes on the same route and same flight schedule if you have them at different flight levels, but since every plane has to land at flight level 10, you'll be just postponing a future conflict.
6. Extra task: As usual, you'll be facing multitasking stuff. This time, a string containing 3 letters and 3 numbers will be presented on the screen for some seconds. You have to memorize it. Then, a voice will call for other similar strings (3 letters, 3 numbers), and if it does match the one you memorized, you'll have to press a button. That's all.
TIP: The best tip I can give you is to stay calm and always keep an eye on the clock. You'll be doing not more than 3-6 things in one minute, but they may be scattered all over the screen so always keep a sense of time (the next minute, those tasks have expired and you have some others).
TIP 2: Just relax, eat well and sleep well. The tests are not difficult and they're not very "intense", but they're big and a bit boring sometimes. So stay alert and feed yourself!