FreshThemes are customizable templates in Freshservice that can be used to extensively change the look and feel of your support portal. They are a collection of style settings that can be configured in your account, including everything to do with colors, stylesheets, and layouts. 

If you are new to Freshservice, follow the steps below to get started with FreshThemes

Do it yourself using the advanced portal customization options

In addition to your basic rebranding options, Freshservice comes with a set of advanced portal customization options to let you define each and every little detail of your support portal. They are found under Admin > Service Desk Rebranding > Customize Portal.