If you have not already installed and configured Elastic APM, the Setup Instructions will get you started.
Index patterns tell Kibana which Elasticsearch indices you want to explore. An APM index pattern is necessary for certain features in the APM app, like the query bar. To set up the correct index pattern, simply click Load Kibana objects at the bottom of the Setup Instructions.
After you install an Elastic APM agent library in your application, the application automatically appears in the APM app in Kibana. No further configuration is required.