What's the problem? Is it because you're uncertain about the length of the car? With small cars like the C2 it can be a problem because instead of the front and end tapering down, they are quite flat, giving the illusion from inside of being longer than they are.
Try as above, driving forwards so the back is roughly lined up at the space you're aiming at and then adjusting the mirrors and reversing in. Sometimes it can help if you're reversing into a marked space - angle the door mirrors downwards so you can see the lines on the ground and you can reverse it in using those as a guide.
Low speed precision manoevres will be hard to master at first but as you practice and get more experienced you'll find them easy.