How to use Perks in Skyrim

I am a level 3 in Skyrim and when I go to the Level Up Option I can see that I have 3 perks, but I don't know how to select which perks I want. Is there a special section in the menu or is there something I'm missing?

You can use WASD to navigate through the constellations for each skill. The perk trees are accessed by zooming in to the constellation using W or by clicking.

I just find out that the game has some serious trouble when you customize the keboard keys, as in my case, in that you can't navigate the skill select screen. So I returned during a while in the preselect keys and all works okay! When you reassign some of the keys it is simply IMPOSSIBLE to select any perk to improve it! Now I finally have been able to use my 8 points.