Can I relocate my iTunes Library to an external drive?

Can I relocate my iTunes Library to an external drive, while leaving the app on the computer? Running mid 2007, 24-inch iMac, OS X El Capitan, 10.11.6. HD is full. I'm thinking I can copy (or back up?) the Library to the external drive and then re-point iTunes to the new location?

I can't afford a new computer right now and can't upgrade this one. It's served me very well for 15 years without complaining. Hate to loose her.