Hi - if you installed the software (by running the Limewire Installer app) you should have it on your hard drive. Do a search for Limewire on your Mac using Sherlock. When you find it, try running it... odds are it is ready to rock.
(When you install Limewire there's a point where you're asked whether to put an alias to the app in the Dock or on the desktop, or not to make one, Perhaps you opted not to make one at all?)
Keith
technical editor, MacUser magazine
http://www.macuser.co.uk/