To add a new plugin you must save the plugins Ruby source file to your Relyze Desktop plugins directory, which by default is located in your documents folder, e.g. C:\Users\USERNAME\Documents\Relyze\Plugins.

You can then instruct Relyze Desktop to “reload all plugins” by opening the Plugin Manager via the main menu (Tools->Plugin Manager) and then right clicking in the Plugins view. Relyze will then add in your newly created plugin.