Have you had a look at our website? We have a variety of getting started materials, including some videos.
You may want to have a look at this Elasticsearch getting started webinar for the basics of how to download/install/interact with Elasticsearch (including a test bed in the Dev Tools)
We also have a book, called the Definitive Guide that while was last substantially updated for 2.x, is largely applicable still for 5.x. In particular, you may be interested in the mappings section.
Then, once you've got a little handle of Elasticsearch, I'd say you may want to check out this Logstash getting started webinar, since Logstash has a Kafka input where you can configure topics to pull from.
We also have a two part blog series on using Kafka with the Elastic Stack that may be of interest to you.