Three on One in Teams - How do I report trolling teammates?

So I got paired up with yellow, we were winning for most of the game and had a favorable position. Then green blunders his queen (or maybe intentionally put it there) and yellow can take it with his knight... except my partner doesn't. He then goes on to waste 50 seconds before making a non-queen taking move. He then puts his queen in a corner where it does nothing and makes no efforts to prevent himself from getting mated. He is the definition of a troll. 

Now that I finished my rant, how do I report this guy?

I was there every second he waited to not take the Q. But I would message one of the admins privately next time.