Skills
Skills are special abilities that you can use.
EP is essentially the equivalent of Mana in Doom RPG. EP is spent on many things, including using skills, quick-charging your Shield, and withdrawing/depositing items into the Locker.
In order to learn and upgrade skills, you must use Skill Tokens. Learning a new skill will only cost one token. To upgrade a skill, you must have the amount of tokens equal to the new level of the skill you wish to upgrade. Skill tokens will be given when leveling up and can also be found in the world.
The Skill Wheel is where you can place skills for actual usage. To assign a skill to the wheel, highlight the skill in the menu, hold the Skill Wheel key, and press and hold the direction of the slot you wish for the skill to go into, then release the key. You may also bind keys to quick use skills, each key corresponding to the indicated skill by the numbers in the wheel.