Adrien just found a ring in his room.. after putting it on, he was introduced by Plagg. Who told him about his powers. And without a second thought..

"Plagg, Claws out!!"

He transformed into Chat Noir and jumped out of his window.. with honestly no idea on how his powers worked yet. He ran over the rooftops.. as he noticed there was danger nearby. He went over there and hid, for a sneak attack.