Obviously this is for the complete beginner, but here it goes.
Updating WordPress is basically an automated process. While the user (you) has to start it with a few clicks, after that everything happens on its own.
The Update Process
Log in to your WordPress powered website. Then maneuver to the Dashboard in the left upper corner.
Then hit “Updates” and this will take you to where you can see all the updates available, not only WordPress but plugin and theme updates too.
If there is an update it will be seen there. In this case click the update button and then wait a few seconds for the magic to happen and that’s it.
If everything runs on the latest version (WP, themes, plugins) then there is a message confirming this. In this case you’re all set, there is no need to do anything.
Before update, officially WordPress raises attention to back up all data because there might be an error during the update process which could result in a data loss.
If for some reason the update doesn’t go through for the first try, try again. Make sure you have a stable internet connection.