Hi Madhouse,
You get as long as you need to practice the computer tests before the actual testing begins, so don't worry too much...
Relative direction test: Imagine an arrow, vertical, with the arrow head at the top. You need to imagine you are now standing on this arrow, facing the arrow head (ie. you are looking 'upwards'). A dot appears on the right of this arrow. Press 1 if the dot is on your left, press 2 if the dot is on your right. Dot moves. Repeat this process.
Sorting task. You are instructed to 'sort' shapes or numbers into categories. You are presented with a picture of a blue triangle. Press 1 if this is a triangle. Press 2 if this is a square. Press 3 if this is a circle. Press 4 if this is a diamond. New shape appears, continue as before. Occasionally the 'categories' will change, so you need to keep an eye on them.
The tasks do get progressively harder (and more complicated), with more 'rules' introduced, but this is the bare bones of it...
Hope that helps a bit!