To unlock the "Summercamp" trophy in Friday the 13th: The Game, all you need to do is join or create an online match and play it through to the finish as a counsellor. It's random whether or not you play as Jason or a counsellor, so this may take more than one try.
Whether you win or lose, die or survive, as long as you stay in the match until the end you will unlock this trophy at the end of the match.