I am running low on memory, 80% of memory is with iTunes...

I am running low on memory, 80% of memory is with iTunes, how do I move my itunes library to an external HD and empty space to my mac? I have 1TB to my mac, a 1TB time capsule - which has a 2TB HD interfaced to it.

I look into the files and see movies, music and itunes - all of these has my movies located in them (movies are 85%) of my itunes memory. I am not sure what files to move to an external HD - if this is the right move to make...

Any suggestions would be greatly appreicated.