Upgrading from previous versions of OS X
Upgrading from OS X Snow Leopard or Lion
If you’re running Snow Leopard (10.6.8) or Lion (10.7) and your Mac supports macOS High Sierra, you will need to upgrade to El Capitan first. Click here for instructions: https://support.apple.com/en-us/HT206886
Upgrading from OS X Leopard
If you’re running Leopard and would like to upgrade to macOS High Sierra, first you’ll need to upgrade to OS X Snow Leopard. You can purchase OS X Snow Leopard from the Apple Online Store.