To take a platform snapshot backup, click into the machine you wish to back up.
The click on the Storage Tab.
You will see a list of Disks, and the Backup option on the right hand side, for each disk.
Click on Backup for the disk you wish to snapshot.
Confirm your choice, and the system will confirm and list all taken and pending backups.
From the Backup Tab, you can restore from a snapshot, or convert a snapshot to a template to replicate / clone a server or to use as a new gold master template.