The Let's Encrypt Easy Certificate Management Integration feature is visible when enabling SSL settings, at Settings > Control Panel > Security Settings > SSL

When SSL is check-marked, the option for "Let's Encrypt SSL Certificate" will be shown.

Select the radio button "Apply Let's Encrypt SSL Certificate", add an email address, then checkmark the Agree and consent checkbox.
Click Save and Restart Services.
NOTE: Terms of Service and Privacy Policy hyperlinks are below the checkbox mentioned above.
