WATCH ALSO:
1.
https://youtu.be/jfDwPZ1c7v4
2.
https://youtu.be/OJ7K86gEkYw
To connect a third-party domain to a Shopify store, navigate to the general Settings / Domains, click on the "Connect existing domain" button, enter your domain name, click "Next" and then "Verify connection". After that Shopify will provide you with DNS data for 3 records (A, CNAME, TXT).
Go to your domain provider, add the DNS records, come back to Shopify, and "Verify connection" again. After that, you will need to wait at least 2 days until everything gets synchronized and starts working.
Check out a dedicated blog post
https://shopifighter.com/blogs/basics/connect-third-party-domain-shopify
00:00 Shopify: Connect Existing Domain
00:25 Domain Provider: Add DNS Record
01:22 Shopify: Complete Verification
01:30 Shopify: Change the Domain Type
01:50 Testing