Freshthemes would be available under the Freshthemes Gallery. You could choose Freshtheme and download it.

The download would contain a folder, with text files containing the code that would go under each section within Admin--> Channels --> Portals --> Customize Portal. You would have to Copy+Paste the content from these folders to those sections accordingly and "Save and Publish" the changes.

The Freshtheme would be published onto your support portal and the customizations would take effect to make your Portal look similar to the Theme.