Download the plugin.
(Optional) If the plugin does not provide a directory structure, create a directory with the plugin name in <game_directory>/red4ext/plugins.
Copy the plugin files as following:
If you have created a directory at step 2, copy the files in the newly created directory.
If you did not create a directory, copy the files in <game_directory>/red4ext/plugins.
(Optional) Start the game and verify <game_directory>/red4ext/logs/game.log if the plugin is loaded correctly.