Creating a basic Audio/MIDI plugin
On MacOS I recommend extracting this to /Applications. Otherwise just extract this to your home folder and maybe add a shortcut to the Projucer.
Install VisualStudio (the full IDE)
Install XCode from the Mac app store and run the following in a terminal to get the developer tools:
xcode-select install
Install Code::Blocks (You can also just use a makefile if that suits your fancy)
Once those are all installed, in wherever you extracted the JUCE folder go to JUCE/examples/DemoRunner/ and open the file DemoRunner.jucer in the Projucer. After that opens, export it to your IDE using the button at the top and build the executable. This will let you run your plugins in a demo environment.