Help with using skills !

Well I read and reread manual but I can't issue this problem : since the beginning, I have 4 skills in the bottom window (the big thing that takes 30% of the screen with useless gauges!!) -> pickpocket, disarm Trap, prowling and repair...
But, now, I need to try something else like lockpicking or healing.

Is there a way (i'm sure there is) to use these skills or change the four in the window ???

Thx for help cuz I'm stuck for some quests.

 

Lockpicketing:
First, you need lockpicks, then either drag the item on to the little hand in the inventory screen or you can place them in the quick slots. The cursor should change and allow you to click on a locked item.

Heal:
Same as above but uses bandages.

 

You can also make your own lock picks if you are a techy and improve it into a skeleton key (or something like that).