Okay,
  I cannot provide much help with Mac OSX, but it's pretty simple.  First, in the server-manager GUI, make sure you have "Remote Access" set to allow FTP.  Then make sure you are in a group that has access to the ibay you want to work in.
  Finally, FTP with your username and password.  This takes you to you user's $HOME directory.  So, you'll need to find the ibays.  They are located in :
/ibays/<ibayname>/
Basically, go back to the root and then work up through ibays and the ibayname.