Any plugins that do not ship with the server will need to be installed as .ez archives by copying them to the plugins directory. Once they have been copied to the correct directory, they will show up in rabbitmq-plugins list and can be enabled with rabbitmq-plugins enable plugin-name.
The plugins directory location is determined by the RABBITMQ_PLUGINS_DIR variable. Its default value depends on how you installed RabbitMQ. Some common values are:
|Installation method||Plugins directory|
|Windows||Typically C:\Program Files\RabbitMQ\rabbitmq_server-version\plugins (depending on where it was installed)|
|Generic Unix||rabbitmq_server-version/plugins (depending on where it was installed)|
The enabled plugins configuration is preserved between upgrades, so there is no need to re-enable plugins after an upgrade, but because the plugins directory changes between versions, any third party plugins will need to be copied to the new directory. It's very possible that due to API changes you may need to check for updates to third party plugins at this point.
You can also build RabbitMQ plugins from source. The sources for a particular version of the plugins is distributed in the same archive as the broker with that version. The source code repositories can all be found on GitHub. See the plugin development guide for more information on building plugins from source.
Note that plugins tend to be strongly bound to a particular version of rabbitmq-server. For example, if you are running RabbitMQ 3.6.6, you should check out all plugins with the Git tag rabbitmq_v3_6_6.