Integrate elasticSearch with EclipseLink
There probably isn't a tutorial for integrating EclipseLink with ElasticSearch. You'll need to develop your own.
Start with the ElasticSearch Java API.
Some people will use Elastic as a database. If you still have a database, then you'll need to keep the ES index up to date with the database. You'll need to hook into the insert/update commands (if possible) and re-index objects as needed.
If it is possible I would recommend you use Hibernate instead of eclipselink as a JPA implementation.
Why not use Elasticsearch directly: The #1 reason is that Hibernate Search integrates perfectly with Hibernate ORM. All changes done to your objects will trigger the necessary index changes transparently. https://docs.jboss.org/hibernate/search/5.6/reference/en-US/html/ch11.html
I also found this tutorial very informative:https://www.youtube.com/watch?v=ufaI51o_7WI