Simple learned abilities do not require a roll, they just happen, according to GM discretion, of course.
Points of proficinecy refer to the amount of which one is skilled in a particular ability. Mechanically, they refer to the number of D6 rolled.
Willpower may not be spent to enhance powers.
Merits allow you to re-roll your lowest die when attempting to perform a related task or skill.
Weaknesses require you to re-roll your highest die when attempting to perform a related task.