Firstly, you will need to access your cPanel and click on Lets Encrypt™ SSL:

Then click on Issue in front of your domain name. If it’s not the main domain, make sure you have it as an addon of the parked domain in your cPanel.

Lastly, choose http-01 validation method and click Issue:

Then, you will see the notification that the SSL Let’s Encrypt has been successfully installed to your domain name. Congratulations!

NOTES: If you found an error when installing - please refer to this article.