For skills (abilities) you have ctrl +, shift + or alt + click.
After putting your first point into a certain skill (simply by clicking on it) you need to assign a key by holding it and clicking on a skill at the same time.
So first you have 1 point to spent:

Once you spend a point, it will show you some value:

Then you just hold a key (in this case ctrl), click on the skill you chose before and it's assigned (on the right)
