Skipped iCloud Keychain configuration during install of El Capitan During installation of El Capitan I skipped the iCloud Keychain configuration because it wouldn't validate the code sent to my phone.

What was this process for and how do I restart it now that the instillation is complete?
Settings > iCloud > Keychain. You should be able to set it up from ther. Make sure your phone is also on iOS 9.