How do I contact Riot?

So I met this guy in one of my games a long time ago. Just recently he contacted me with a website, so I asked what it was. He then said that it was a website for free RP. I told him that he shouldn't be doing that, and that it's technically stealing from Riot. He said that it was fine, and that he doesn't worry about it. I haven't visited the website because one: it's wrong, and two: I've heard Riot bans people who use those websites. So my question is, how do I contact Riots support teams, so I can tell them about this whole thing? Thanks!