Well, to join it you just need to find the Temple of the Grandmaster fanclub which shouldn't really be that hard and ask the boss to add you, something that might not happen at all since he is kinda... Gone (not literally tho lol). Still, you don't need to be "added" to hang around the fanclub so yeah.
If you want to prove what you said, the best way to do it is to make a proper thread dedicated to it. For this, just go to the new posts tab and click on the right side where it says "Post thread".
Last but not least, if by PM you mean Private Message, just tap/click on the name of the user that you want to PM and hit the "start conversation" button.