To update your WordPress version, you need to first log in to the admin area of your WordPress website and go to Dashboard » Updates page.
You will see a notice that a new version of WordPress is available. Now you just need to click on the Update Now button to initiate the update. Just wait for the process to unfold on your screen and wait for it to finish.
You should make backups or have a WordPress backup plugin before doing these updates, especially if your website has important files and is not a new site.