You can change your base theme used for your website via the DESIGN menu > Change to a new look and feel.
This will take you to an option to select from one of the preset templates.
Each Theme has a series of buttons under it.
Clicking the SELECT button will take you to a Confirm new look and feel page, where you can apply the template.
You are presented with a series of options of elements to apply, the default options are recommended but you can change banner and logo images as needed.
It is recommended that you use the DESIGN option > Back up your current theme, as it allows you to add your own custom title for the backup, but you can also check the Backup current design settings? checkbox on this screen.
Restoring a saved theme
To restore your website to a saved theme click the DESIGN menu then Back up your current theme.
This will provide both the option to backup the theme, and a list of previous backups to restore.
Click the RESTORE NOW button next to the theme you want to restore, this will replace the current theme with the backup.
If you have more than one website under the account you can choose to apply the theme from the other website.