@ikakavas, Thank you for your response.
Below are the changes and configuration which is done by us:
We have added the below 2 line in  elasticsearch.yml  file:
xpack.security.enabled: true
xpack.security.transport.ssl.enabled: true
And set the password for all built in user. Now when we are trying to query our elasticsearch we need to pass built in user and password then its working. As shown below:
curl -XGET -u elastic:admin@123 http://192.168.56.4:9200/
We have added the below 2 line in our  kibana.yml  file:
elasticsearch.username: "kibana"
elasticsearch.password: "admin@123"
And now we are able to access the kibana dashboard using username  elastic  and its password. We are able to see security feature on dashboard and able to create new user also using  users and able to login using that user.
We are able to see the old logs also on kibana dashboard.
But now we are facing issue that new logs are not reaching over kibana dashboard. Its seems that logstash is not sending logs to elasticsearch. We have made the below changes at logstash:
Added the below 2 lines in  logstash.yml
xpack.monitoring.elasticsearch.username: "logstash_internal"
xpack.monitoring.elasticsearch.password: "admin@123"
Below is my logstash configuration file
input {
  beats {
    port => 5044
  }
}
filter {
  if [type] == "syslog" {
    grok {
      match => { "message" => "%{SYSLOGTIMESTAMP:syslog_timestamp} %{SYSLOGHOST:syslog_hostname} %{DATA:syslog_program}(?:\[%{POSINT:syslog_pid}\])?: %{GREEDYDATA:syslog_message}" }
      add_field => [ "received_at", "%{@timestamp}" ]
      add_field => [ "received_from", "%{host}" ]
    }
    syslog_pri { }
    date {
      match => [ "syslog_timestamp", "MMM  d HH:mm:ss", "MMM dd HH:mm:ss" ]
    }
  }
}
output {
  elasticsearch {
    hosts => ["192.168.56.4:9200"]
    user => "logstash_internal"
    password => "admin@123"
    sniffing => true
    manage_template => false
    index => "%{[@metadata][beat]}-%{+YYYY.MM.dd}"
    document_type => "%{[@metadata][type]}"
  }
}
When i am restarting the logstash service getting below error log:
[2019-06-11T17:52:37,338][WARN ][logstash.outputs.elasticsearch] Attempted to resurrect connection to dead ES instance, but got an error. {:url=>"http://logstash_internal:xxxxxx@192.168.56.4:9200/", :error_type=>LogStash::Outputs::ElasticSearch::HttpClient::Pool::BadResponseCodeError, :error=>"Got response code '401' contacting Elasticsearch at URL 'http://192.168.56.4:9200/'"}
[2019-06-11T17:52:38,307][WARN ][logstash.outputs.elasticsearch] Error while performing sniffing {:error_message=>"Got response code '401' contacting Elasticsearch at URL 'http://192.168.56.4:9200/_nodes/http'", :class=>"LogStash::Outputs::ElasticSearch::HttpClient::Pool::BadResponseCodeError", :backtrace=>["/usr/share/logstash/vendor/bundle/jruby/2.5.0/gems/logstash-output-elasticsearch-10.1.0-java/lib/logstash/outputs/elasticsearch/http_client/manticore_adapter.rb:80:in `perform_request'", "/usr/share/logstash/vendor/bundle/jruby/2.5.0/gems/logstash-output-elasticsearch-10.1.0-java/lib/logstash/outputs/elasticsearch/http_client/pool.rb:291:in `perform_request_to_url'", "/usr/share/logstash/vendor/bundle/jruby/2.5.0/gems/logstash-output-elasticsearch-10.1.0-java/lib/logstash/outputs/elasticsearch/http_client/pool.rb:278:in `block in perform_request'", "/usr/share/logstash/vendor/bundle/jruby/2.5.0/gems/logstash-output-elasticsearch-10.1.0-java/lib/logstash/outputs/elasticsearch/http_client/pool.rb:373:in `with_connection'", "/usr/share/logstash/vendor/bundle/jruby/2.5.0/gems/logstash-output-elasticsearch-10.1.0-java/lib/logstash/outputs/elasticsearch/http_client/pool.rb:277:in `perform_request'", "/usr/share/logstash/vendor/bundle/jruby/2.5.0/gems/logstash-output-elasticsearch-10.1.0-java/lib/logstash/outputs/elasticsearch/http_client/pool.rb:164:in `check_sniff'", "/usr/share/logstash/vendor/bundle/jruby/2.5.0/gems/logstash-output-elasticsearch-10.1.0-java/lib/logstash/outputs/elasticsearch/http_client/pool.rb:157:in `sniff!'", "/usr/share/logstash/vendor/bundle/jruby/2.5.0/gems/logstash-output-elasticsearch-10.1.0-java/lib/logstash/outputs/elasticsearch/http_client/pool.rb:146:in `block in start_sniffer'", "/usr/share/logstash/vendor/bundle/jruby/2.5.0/gems/logstash-output-elasticsearch-10.1.0-java/lib/logstash/outputs/elasticsearch/http_client/pool.rb:128:in `until_stopped'", "/usr/share/logstash/vendor/bundle/jruby/2.5.0/gems/logstash-output-elasticsearch-10.1.0-java/lib/logstash/outputs/elasticsearch/http_client/pool.rb:144:in `block in start_sniffer'"]}
Can you please help me whats mistake i am doing here?
Thanks.