how do i upgrade
I would like to install garageband but everytime i try keep seen my computer need upgrade
iMac
What Mac do you have (model, year)?
What version of OS X do you have?
Every Mac should come with some version of Garageband: this will either be on the disks that came with your computer, or should be available in the Mac App Store under your AppleID.
The latest version of GarageBand will require Mavericks. You should check whether your Mac can run that, and if so, it should be a free update.