That is the problem. You shouldn't have to worry about 'placing them in the correct folder' when you download a plugin, you just drag the plugin folder to your "Main Game DIrectory" it will merge accordingly. You are making this harder than it needs to be.
TLDR: Don't go into the plugin folder. The only folder you should be opening is just the main game directory. Literally drag the folder that you downloaded called plugins and just drag it to main game directory. It will create folders for you if you don't already have them.
Video info if you need more help for callout manager and a few callouts: