Reporting A Toxic Player

I am looking to report a player that was recently toxic to me in post game lobby chat. Not only were they toxic post game, but we had a Fiddle mid who was afk at the start and this player (Yasuo) claimed that they were a duo and to not vote for a remake because he was coming back. Then we found out later in the game that he was lying about knowing him and being in a duo. This obviously created a toxic environment during the game. (fiddle never entered the game).

Anyways, I have a screenshot of the post game convo and I am just wondering where I can share this and how to report this player?