There is a section in the forums for each world...Arendyll, Winyandor, and so on. There is a section of fellowships seeking members and members seeking fellowships under the world name. That is an excellent starting point. Fellowships can also be found under the fellowship tab. (Your global ranking number may be found on your main city page, beneath your avatar and your name.) Click on that, then on the Fellowship tab.) Look for fellowships with members who have a similar ranking to yours. Then, send a message to the archmage (the fellowship's leader) and ask if they have room (send a message by clicking on the person's name and then clicking the messaging tab.)