Elasticsearch query plugin

I'm upgrading an Elasticsearch plugin from version 2.4.0 to 5.4.0. This plugin implements a custom query but with the new changes on Elasticsearch Java Api I'm a little confused in how to register the new query. I search in Elasticsearch site and I found that I must implement the SearchPlugin interfaces and override the method getQueriesbut I'm still confuse and how I do that. Any help?