Warning: by default, you should be making a full backup before upgrading the WordPress core software to a major release WordPress version.
You do not need to make a full backup before upgrading to a new minor WordPress version, or before upgrading themes or plugins.
A major WordPress version is dictated by the first two sequences. For example, 4.9 is a major release. So is 5.0, 5.1, all the way up to 5.3.
A minor WordPress version is dictated by the third sequence. Version 3.9.1 is a minor release. So is 3.8.2. A minor release is reserved for fixing security vulnerabilities and addressing critical bugs only.
Making a backup through your web hosting control panel.
In most cases, you should be able to reach the web hosting control panel @ http://www.yourwebsite.com/cpanel
When you signed up for web hosting, you will have received your web hosting control panel username and password. Use this at the login screen.
Once logged into cpanel, find the Files section, and select Backup Wizard:
At the Backup Wizard section, click Backup:
On the next screen click Full Backup.
On the next screen, keep “Home Directory” in Backup Destination, enter your email address, and click Generate Backup.
When the backup has completed, you’ll receive an email like this:
How do I know updates are available?
Login to your WordPress admin section, and look for a number at the top of the screen, highlighted in green below:
Click either button, to be taken to the WordPress Updates page
In the case above, there is an update to the plugin “Gravity Forms”.
I select the box to the left of Gravity Forms, and click Update Plugins.
The following screen will load:
If there is still an indication that further updates are available, click “Return to WordPress Updates page”, and follow the prompts to update any further themes, plugins, or updates to the WordPress core software.