You are either a "good" player or a "bad" player. Whichever you are, you are obliged to vote once per day, by posting in bold in the thread. eg. Vote Tamius. You may Unvote and Vote someone else as many times as you want, and the player with the most votes at the end of the day is brutally killed by everyone, that is, "lynched". If you are a werewolf, you may send in a "hunt" order by Private Message to the GM. The GM runs the game.
All orders must be in before the deadline, or they are ignored. It is considered that everyone votes during the "day." and the wolves hunt during the "night." Normally most games begin with a "night deadline", a day in which the votes are ignored (known as "day zero sham voting") and only the orders, by the wolves and other roles which send orders, are considered.
There are a multitude of roles in the game of Werewolf, and they are listed at the start of a game thread, with their effects. Some players may also have traits.
For the villagers and other "good" players to win, they must kill all the "bad" players. For the "bad" players to win, they must kill all members of opposing packs (generally there are two packs, occasionally three) and then reach the same numbers as the remaining "good" players. This is called parity, and when baddies of one pack are equal or greater in numbers than goodies, they win.
To sign up to a game of werewolf, post in the thread. A simple "In" will suffice, and you will be added to the player roster by the GM.