Simply click on the icon and you will be taken to the main backup admin area.
Alternatively, you can navigate to the backup components in Joomla by navigating to
Components > JoomlaPack
From here click Backup to start the backup process.
Write a quick comment about the backup that you are doing and then hit the BACKUP NOW icon.
The backup will take several minutes and you will not be able to do anything else in the admin area until the back up is done.