Music on External Drive Setup

I cant figure out how to make this work. I have a Mac, 2ghz Core i7, 16GB mem. My Music catolog is 30,000+ songs (166.54 GB), 20GB Movies, 360 GB TVshows, 45 GB Audiobooks, and 40gb podcasts. Pretty big. They all sit on an external drive. I cant figure out how to set up Tune span. I would like to fix the consolodation problems in my library. Please let me know how to make this work. Thanks in advance Robin