i had to do the reverse park to get my p's, what ever you do never hit that gutter, its better to be further away from the gutter because you will only lose a couple points which is better than instant fail. this might help you but of course its way easier to show, this is what my instructor taught me and it works perfect everytime. ok here it goes:
drive past the spot you want to reverse into and line up with the car beside you, put it in reverse (of course) do one full turn of the steering wheel to the left and start moving backwards until you get to an appropriate angle, next turn the wheel one full turn back to the right and keep rolling backwards until you can see that the front of your car wont hit the back of the other also if done right your back tyres should be close to the concrete part of the gutter, than the final step is to do another full turn of the wheel to the right again and boom if done right you should fit into that parking spot perfectly. if you had a couple more days to practice this you will be fine, so if you can before your test get out and practice now lol.