In general, you just need to extract the zip file and put the content in the root directory of the application. This root directory is
In order to upload files to your server you can follow the steps detailed in this guide: How To Upload Files To The Server With SFTP?.
Once theme files and folders are uploaded to the instance, open the Magento admin panel and you should be able to activate it.
Anyway, we highly recommend our users to look for information in more specialized forums when they have problems related to the Application or how to customize its content.