How to report "Riot Piont Hack" cheating?

I am new to League Of Legends, being 42 years young I'm a little straighter in my ways than most. After playing for a week I recently got asked to join a team. I joined and a week later got a message "RP hack". I thought no wonder I've been taking a good hiding recently, so I mentioned this. The reply I got was a link, then instructions to put passwords in. I was dismayed & typed in "no thanks". Then the player has disappeard off my friends list, but I am still in the team. Can somebody help as I have tried been the goody two shoes in reporting this to riot games but can't find the correct option. It might be obvious to some but I have had lack of sleep this week & I am struggling to think with any clarity! After this message I shall leave the team. I could of entered the link for this message but I think that wouldn't be fair to Riot Games, but I have saved it.