Mac mini, Mac OS X (10.6.8) < your profile
You need to be running v10.7.2 Lion.
Make sure your mini meets Lion General Requirements
You can purchase and download Lion from the App Store that is already on your Mac since you are running v10.6.8
You can locate the App Store app either from your Apple menu, the Dock, or the Applications folder.
Or you can purchase the Lion thumb drive here > http://store.apple.com/us/product/MD256Z/A