When you login it will tell you if you are in the Tribunal in this case I am in the tribunal but if you want to know who else is in the tribunal all you have to do is type /tribunal.
The Tribunal are The top 5 players that have played at least 30min Yesterday.
Once you have verified that you are in the Tribunal here are the other things you need to know. To talk to Tribunal members you use the /x <message> or use the Tribunal chat tab to talk to Tribunal members only about things that need approved and such.
This is the window that pops up when you type /tribunaltasks, in this case I use the filter plot (the filters are PLOT, UNCLAIM, ITEM, MONSTER, or PORTAL) so you would type /tribunaltasks plot.
Circled in blue is the task number. This task number is used to do 2 things approve or decline a task. To approve a task such as land becoming plot you would type /tribunalapprove <task number> and to decline a task you would type /tribunaldecline <task number> . You can not approve your own tasks nor for another characters on your account.
To remove or decline a land that is plot (like a training rooms etc..) you type /tribunalunclaim when your standing on the land but you still need 3 votes to get the land unapproved. Also /tribunalplotclaim sets up a land parcel for PLOT. It still needs 3 tribunal members to approve it. A prime Example of a training room Monster is fenced in so it can't attack you directly this would be a magic def training room.