I actually disagree with the above posters. The beauty of a free form amino acid supplement is that no digestion is required so it is immediately absorbed into the blood stream. The timing will make a difference.
BCAA are very anti-catabolic and signal muscle protein synthesis. They are best to supplement with before/after workouts and before catabolic events like fasted cardio.
If you are training fasted they can help (if you are trying to add mass). Besides that, you wont need them if you are eating a pre workout meal that includes protein.