How to register 3rd party domain on lightsail wordpress instance

Say you've purchased mydomain.com through a registrar, first things you would do is setup a DNS zone with that registrar, whose A record for mydomain.com points to the IP address of your Lightsail instance, and maybe also a CNAME for *www.mydomain.com pointing to mydomain.com

To get an SSL cert, in the Lightsail documentation the instructions for creating TXT records are Lightsail-centric but should be able to be easily applied to other registrars.

Look at Step 4: Add TXT records to your domain’s DNS zone in Lightsail of https://lightsail.aws.amazon.com/ls/docs/en_us/articles/amazon-lightsail-using-lets-encrypt-certificates-with-wordpress#add-a-text-record-to-your-domains-dns-zone-lets-encrypt-wordpress

Adding a TXT record to your domain’s DNS zone verifies that you own the domain. For demonstration purposes, we use the Lightsail DNS zone. However, the steps might be similar for other DNS zones typically hosted by domain registrars.

Follow the steps to create TXT records that you are prompted to create, but instead of doing this in the Lightsail console, create TXT records with these values in the tool that you use to create & update DNS records with your registrar.

The case im dealing with is this; I have a wordpress site in lightsail. This site only has a statis ip. There is no domain for it as yet. I want to install SSL with lets encrypt on this Wordpress site to test somethings. i have a domain registered with godaddy. I wanted to use that domain as the root domain to install the SSL on the wordpress site on lightsail. I went through the instructions on lightsail on setting on a DNS Zone. when i added the name records to godaddy it took down that website. I am trying to find a work around to installing the SSL without bringing down the parent site.