The instructions here explain how to create an SSL certificate with Let’s Encrypt. Let’s Encrypt is free and widely supported by most website hosting companies. It also explains how to create a WordPress website from the website hosts control panel, cPanel, in this instance. Website hosting companies may not use cPanel so the instructions for both of these could be different but the end result is the same. When an SSL certificate is installed when a WordPress site is created, and the default website name includes https://, all posts and pages for the website will be encrypted.
For websites that are already operational, they will need to be upgraded to SSL. The best thing to do is to try to create an SSL certificate using Let’s Encrypt and contact your website hosting company if you have difficulty. They do this all the time and it is very easy for them. To upgrade the website’s WordPress Address (URL) and Site Address (URL), you usally have to update the database with phpmyadmin. Some plugins can do this programmatically so you don’t have to.
Additional note: If you install a plugin, only get it from a source you trust like WordPress.org, you pay for it (so now you own it).
OPTION 1. New WordPress website encryption
OPTION 2. For an Existing WordPress website. Manual installation
Here is another way of encrypting a WordPress site, though it is a little more involved, some website hosts that have not adopted Let’s Encrypt yet, you will need to do it like this. First you need to install the plugin from WordPress.org, which can be accessed from the wp-admin plugins page. You can also download it from WordPress.org but not recommended. Definitely do not install it from anywhere else.
WP Encryption WordPress SSL Plugin – Install free Let’s Encrypt SSL Certificate on cPanel 2020
WP Encryption – One Click Instant Free SSL Certificate & Force HTTPS
OPTION 3. When you already have a certificate, but the content on your website doesn’t use it. For that you can install a plugin that automatically upgrades pages for you:
Other options are available but not mentioned here. Final caution: if a plugin requests you to share information with its creator, do be careful and understand what they are requesting and why.