You can buy more licences for your account or upgrade the storage space if you need to, no matter what type of account you have.
Do this:
1: Log in to the website
2: Click on the icon in the top right corner and select "Account settings"
3: Click on "Subscriptions" in the left menu and on "Price plan" at the top.
4: Select whether you want to extend Backup Licenses or Sync Licenses in the lists
6: Press "Update" to confirm
If you don't see any options for upgrading, send us a ticket and we'll help you.