http://dnbible7sqskwppgaqohboxz7u5kzffjzdx3lxzpjtt3s6tzeiytb5ad.onion/bible/operating-systems/tails/backing_up/index.html
If you already have Tails cloned you can jump down to the backing up Persistent Storage section below Note 2: This part will NOT backup your persistent! You must clone tails before you can backup First login to the tails USB you want to backup. Once you are logged in to Tails plug in your USB stick that will serve as your backup.