how do i upgrade my mac from a 2008 version

the latest macOS that a 2008 iMac can run is El Capitan 10.11.6

if you have an earlier OS click here>> OS X El Capitan 10.11

Your post tells us nothing. Do you want to update the Mac OS version? If so, what is the current version? Do you want to get a new Mac and upgrade?

Please add more details.

Cheers,

Jack