To make a backup, go to Tools > Backup from within your account. Choose your backup key options (see below) then click Continue. Once your backup is ready to download, you should see a Save to Diskbutton. Click that button and your backup will download to your computer. That's it. Make sure you save your backup in a safe place, and that you remember where you put it.
Passpack backups are encrypted. That means that no one can read your backups without your Packing Key, making it safe to store these on your computer.
Selecting a Backup Key (optional)
By default, your Packing Key is used to do this encryption - but you can also set a different Backup Key if you'd like. If you're not sure, leave the default. Otherwise, select the I want to provide a different Backup Key option. TheBackup Key is a key that is different from your Packing Key: setting a specific Backup Key can be useful is a variety of situations. The most common which comes to mind is when you want to move data between accounts:
You would make a backup with a Backup Key from the first account. Then, in the second account, use the restore function to fill that account with the backed up data. You can safely swap data this way with another person without revealing your usual Packing Key.
If you choose to use a Backup Key, two fields will appear. Type in the Backup Key that you'd like to use - it must have a quality rating of 64 or better (actually 128 would be best) then repeat it to make sure you haven't mistyped.
Will the Backup Include Shared Passwords?
The backup will include all passwords that you own. That means that if you created a password, it will be backed up. It doesn't matter if you are sharing it with someone else or not.
Passwords that someone else created, and are shared with you, will not be included in the backup.
Can I Backup Settings, Messages or People?
No, as of now, just your password entries and relative tags will be backed up.