About reporting a player

Hey guys, can someone tell me is there any place where I can report a player ? I had a situation, 1 hour ago with a random guy who was insulting me in champion select for no reason. To make things even worse, his name is also forbidden (but he used some different letters), and it is for sure against the rules. He also troll-picked even it was a ranked game. So, a couple violations in just a few seconds. I took a screenshot and would really like to report. Btw I dodged the game, so I couldn't report him after the game. Thanks in advance.
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