how do i leave my guild? i joined mine to be with people untill my guildmates got the game. now i cant figure out how to leave.. help.. THX

Hey guys! its my first time playing an mmo. so i wanted to take it slow and play by my self without alot of people, so i clicked on a light server. but now i got the hang of it and want to play with others, but i cant figure out how to change serevers. if someone could help that will be great.