These are the instructions I followed from this link:
https://codex.www.ads-software.com/Upgrading_WordPress
Step 1: Replace WordPress files
Get the latest WordPress. Either download and extract it to your computer or download it directly to the server.
As a reminder, to extract a tar.gz to a folder use this command, replacing (folder name) with the name of your folder: tar -xvzf latest.tar.gz -C ./(folder name)
Delete your old wp-includes and wp-admin directories.
Copy the new WordPress files to your server, overwriting old files in the root, except perhaps the wp-content folder (see “NOTE” below). You may use FTP or shell commands to do so. Note that this means *all* the files, including all the files in the root directory as well. If you use the default or classic theme and have customized it, then you can skip that theme.
NOTE The wp-content folder requires special handling, as do the plugins and themes folders. You should copy over the contents of these folders, not the entire folder. In some cases, copying the entire folder may overwrite all your customizations and added content.
Also take care to preserve the content of the wp-config.php file in the root directory. This file contains current settings for your existing installation, e.g. database sign-in information. Occasionally new versions of WordPress add statements to this file. (E.g. in version 2.5 the SECRET_KEY variable was added, see Extended upgrade instructions). Compare your existing file with the new installation file which is named wp-config-sample.php. Either transfer your settings to the sample-file and rename it to wp-config.php or copy the new statements from the sample file into your current file.
Step 2: Upgrade your installation
Visit your main WordPress admin page at /wp-admin. You may be asked to login again. If a database upgrade is necessary at this point, WordPress will detect it and give you a link to a URL like https://example.com/wordpress/wp-admin/upgrade.php. Follow that link and follow the instructions. This will update your database to be compatible with the latest code. If you fail to do this step, your blog might look funny.
Step 3: Do something nice for yourself
If you have caching enabled, your changes will appear to users more immediately if you clear the cache at this point (and if you don’t, you may get confused when you see the old version number in page footers when you check to see if the upgrade worked).
Your WordPress installation is successfully upgraded. That’s as simple as we can make it without Updating WordPress Using Subversion.
Consider rewarding yourself with a blog post about the upgrade, reading that book or article you’ve been putting off, or simply sitting back for a few moments and let the world pass you by.