Before you decide to upgrade your WordPress version, please read my article on whether to upgrade your WordPress version or not.
If you decide to go ahead, below are the step-by-step guide on how to go about it:
Step 1: Download the latest WordPress version.
Step 2: Unzip the new WordPress version
Step 3: Backup your WordPress database in case something goes wrong during the upgrading process. I suggest that you use a WordPress database backup plugin which you can download here: WordPress Database plugin
Step 4: Unzip and upload the plugin to your …