After downloading the ZIP file and unzipping it, and looking for a readme file, I opened the only obvious choice which was "DeDRM_Help.htm". It has a section on installation, but it only says "You have obviously managed to install the plugin, as otherwise you wouldn’t be reading this help file." Not really helpful :-) I assume the author of this document assumed that this document would only be accessible to people who have successfully installed the plugin.
I suggest you add a readme.txt file to the distribution with the text "How to install. In Calibre, go to Preferences > Plugins > Load Plugin from File. Afterwards, click Apply, and then restart Calibre. Requires Calibre 5."
If you're talking about one of the pre-release betas, it is the DeDRM plugin only. Don't unzip it. Install the whole file. The complete releases have readmes. Here's the one with install instuctions.
After downloading the ZIP file and unzipping it, and looking for a readme file, I opened the only obvious choice which was "DeDRM_Help.htm". It has a section on installation, but it only says "You have obviously managed to install the plugin, as otherwise you wouldn’t be reading this help file." Not really helpful :-) I assume the author of this document assumed that this document would only be accessible to people who have successfully installed the plugin.
I suggest you add a readme.txt file to the distribution with the text "How to install. In Calibre, go to Preferences > Plugins > Load Plugin from File. Afterwards, click Apply, and then restart Calibre. Requires Calibre 5."