How do i report someone??

How do i report some player who is just and ******* for no reason ?

Basically, i got in rdf and get in a fos dungeon in progress, the moment i enter to could see that the tank was already mad, he probably kicked the previous dps for the same reason he kicked me. So the group go and killed mobs, advancing, and then, the tank got absolutely mad because i was doing less damage than him, even with the fact the he had 6200 GS and i had 4100 GS. He then kicked me, and i ask him what did i did wrong, and he answered:

I was really in shock, I didn't expect this to happen so randomly like that. I also tried to apologize because i may be doing less damage than i should maybe, im not a veteran in the game, but he ignored me. I tried to report him ingame but i didnt find a tool to report someone ingame, so i came here.

You can report them to a GM using an in-game ticket. We have a guide for that here.
Also, please keep related pictures off the forums in the future.