Basically you should unzip the file in C: then you’ll get this folder,
Delete the zip file, and then add up the path as you did, after adding up the path you could call the sen2cor from the console as I mentioned in the previous post,
For more details about the plugin, please take a look at the following thread,
It’s also explained under following item,
4.1New stand-alone installers(since release 2.4.0)
In here,
Also please take a look at following (Edit and add path in windows)