When should I take my protein shakes?

I am 17 and i have just bought some protein powder. I am skinny and I am 6 foot and i weigh about 74lbs. At the moment i workout on monday, have football training twice on tue, a match on wed, 2 trainings on thru, 2 matches on sat and training on sun. i also workout on friday sometimes. Should I take the protein or should i wait until i get more time to workout when my football os over? and when should i take them? and how often? thanks