I'm guessing you may not have much experience with shotguns or handguns...read the two books (or is it just one nowdays? A few years ago it was one for PAL, and another for RPAL), learn it, know it.
There's a multiple choice test with lots of questions, 100 I think, and also there's a practical, where you will have to demonstrate safe handling, loading, unloading and use of many different examples of firearms. When I did mine, I had to show competence with:
-bolt action hunting rifle (Savage .300 win mag?)
-lever action rifle (a Winchester style rifle)
-Mossberg pump 12gauge model 500
-double action revolver (Ruger GP-100)
-single action revolver (Colt single action army)
-double action automatic handgun (CZ-75)
-single action automatic handgun (Colt Gold Cup 1911)
But the books are also interesting from the point of view of learning about guns you maybe aren't aware of much, for instance there's a section dealing with the principles of shotgun patterns and chokes. Or an entire section dedicated to black powder firearms like muzzle loaded flintlocks and caplocks. It's worth the read!