The trait and cognitive theoretical approach to the study of personality entails that there is a way to analyze human personality by extrapolating the salient attributes that makes each person unique. Additionally, trait theory attempts to measure such attributes, predict them, and perhaps correlate them to either a) inheritance, or b) environmental input.
All this being said, "free will" would be explained through a traits perspective as having the choice to perform an action based on the behaviors that mold our personality. The problem with this is that if we have molded our personality to be negative, destructive, and self-harming, chances are that our free will be used negatively as well. Personality is molded by motivation, actions, choices, and social imitation. When we exercise free will we put all of these factors into action in order to create something new. It is entirely up to the way in which our personality directs our actions that we will use free will positively or negatively. It can actually turn out to be a vicious cycle of negativity, or a successful cycle of positivity, depending on how we apply our personality towards the use of free will.
Determinism is the assumption that inherited and biological traits directly and terminally prompt our actions and thoughts. Hence, there is no way around it; we act the way that we are meant to act. Under a traits perspective, determinism will be the ultimate factor that decides our personality. Therefore, it could be assumed that the good will always turn out to be good, and the bad will turn out bad since we are determined by nature this way. However, there is enough research to prove that this is not the case: children of abusive parents do not all become abusive parents, and children of good parents do not always come out to be "good". Therefore, it is safe to conclude that the traits perspective explains determinism as the "tendency" to behave in a certain way UNTIL operant or classical conditioning strategies are put in place to change such tendency. We can all turn out to be as successful or as big a failure as we wish to be if we dedicate time, choices, and methods to do so.
Therefore, the traits perspective explains free will as the personal choice to perform any action within the parameters of our personality and behavioral tendencies. Determinism will be the opposite: the inherent tendency to behave in a certain manner due to inherited traits that can be conditioned to operate properly under optimal circumstances.