http://fanzone.playonline.com/lscom/index.do

Click on Login.

Click on Establish/Join Community. Do not login at this point.

Type in your ID/Password and click Login.

Select the character(s) you want to configure. I recommend doing them all.

Normally if you aren't registered/established with a community, a option is given to register/establish. You will get a screen that looks like this if you are fully set up. If you do not see your linkshell listed, that means you need to get a shell/sackholder to come to the site and 'establish' the linkshell.
All that is left is to set your profile information to Public.
How often does the Linkshell Community update profile data?

In other words, logout of FFXI to put yourself on a queue to be updated.
If anything I said here is inaccurate, please send me a PM with corrections.