You will find people sharing themes here.
If they uploaded the zip or rar file, that is the file you need to download and unzip into your Turing Smart Screen folder.
You need to restart the application for the newly "installed" themes to show up.
If the person who shared did not upload the zip/rar file, you can request them to send them to you. This is why you see people providing their email address to the sharer.
Alternatively, create your own or modify an existing theme using the application's theme creator.