You have to provide the decryption key when trying to logging on to your online storage account. You will find this key on the two USB sticks that come with Zettabits Pro, or you can extract the key from the zBox's local web interface.
Once you're logged in, you can access all shares you defined on your zBox...
...however, you can only access and download individual files if you use the web interface. This is nice to access few files, but annoying if you need to get a large number of files.
After clicking on a particular file you can download it to your PC.