When you arrive on the GitHub page linked above you need to click/select 'release', which sits centrally on the navigation bar above the individual file/package names. This takes you to another page where you can click and download the 'Simple' folder, which contains V1 of this Clover theme.
I've tried uploading the theme folders manually into the relevant place in the EFI folder and most weren't detected by Clover on boot up. I've also tried using CTM, and as per your advice, installed XCode and ran the updated CTM version, mounted the correct EFI partition, installed the themes I wanted with CTM, restarted the computer, ran Clover, and in Options was able to select the theme I wanted, then hitting return a few times, Clover reloads the theme and all looks well but when I restart the computer, Clover goes back to 'Embedded' again.
Right! Got it! I was on the Themes Editor screen and it wasn't saving any changes to the config.plist so yes I needed to be on the GUI screen and enter it in that field. I tried editing the config file manually just now also which is effectively the same thing and also worked. Thanks again! :-D