1. Download the plugin from the github repo / Itch.io page
2. Extract the .zip file
3. In order for Godot to see the plugin, the plugin folder has to be in the “addons” folder, which is directly at the root of your project directory.

Either :

1. Create a addons folder if you don’t have one already
2. Put the plugin folder into the addons folder

1. Go to projects -> project settings -> plugins and enable the plugin.

1. If it seems that you can’t use the plugin yet (like if some features of the plugin aren't appearing), restart Godot and it should work.