(Update 2020-04-24: About two years after the making of this article, some of the content has changed, specifically regarding software updates for the GCP Click-To-Deploy VM, as well as different prompts from LetsEncrypt. The post has been updated to reflect the changes.)
This is part 3 of a three-part guide to setting up and configuring WordPress hosted on Google Cloud Platform and registered with a Google Domain URL. Readers should make sure their WordPress instance is running and behaving properly using GCP, have WordPress admin access, and registered their custom domain (eg http://www.example.com) before attempting this section.