Hey @Amitittech
For upgrading between minor versions you can simply do a rolling restart, instructions of which can be found here: https://www.elastic.co/guide/en/elasticsearch/reference/current/rolling-upgrades.html (Essentially stop node, upgrade, start node; rinse & repeat, but the docs have some extra recommended steps)
You should also check out the breaking changes introduced in 6.5.0 and see if they're relevant to your setup: https://www.elastic.co/guide/en/elasticsearch/reference/current/release-notes-6.5.0.html