repobee-plug is a package for creating plugins for RepoBee. If you just want to use plugins created by others, then you're in the wrong place and should head over to plugins. If you want to create plugins, you are in precisely the right place! I recommend you read through all of the general documentation, and then refer to the parts of the module reference that you need for your plugin.
Don't hesitate to get in touch if you need help, you can use the issue tracker or find contact details on the official web site.
overview creating_plugins code