We ran a couple of instructional posts on how to move a site to HTTPS on the Joomlatools blog. The second post in this series explained how to use Let’s Encrypt on Plesk.
A lot of our customers use a control panel like Plesk to host their websites. There is now a Let’s Encrypt plugin available that allows you to switch sites to HTTPS freely in a few clicks.
Note that this tutorial focuses on Joomla but this applies to any type of site.
If you’re interested you can read the tutorial on the Joomlatools blog: Secure Joomla with Let’s Encrypt on Plesk