Starting of, I think you will find our documentation very helpful. Most of your questions can be answered with information from there and this will also enhance your understanding of how and why things are set up in a certain way. You can search on www.elastic.co for any topic that you want to learn more about !
But these steps are for local user authentication only right?
These are builtin users which are kind of special local users ,not users of the native realm. Our documentation covers both in detail, please read through User authentication | Elastic Stack Overview [7.4] | Elastic
You need to configure at least one so that kibana can communicate with elasticsearch, this user is the kibana user.
If i want to use custom user accounts and we have those in AD then how do I give every individual access to kibana dashboards? Consider I have 50 users
You would need to give the users the necessary roles .read through Granting access to Kibana | Kibana Guide [8.11] | Elastic. when you have the roles ready, you can assign the roles to users in your roles.yml file that you already have
One more question clicked here, are all these account names mentioned in link that you posted are service accounts? and they should also be created in AD as is?
No, these are builtin users ,they exist in elasticsearch, you dont need to create them in AD.
If I want to use keystore then how do I mention here?
I think he meant to say reserved realm == builtin users
You can ask here or your support engineer if you have a subscription. People im this forums will try to answer when we have time, but it's on a best effort basis !