I as well need assistance with connecting my facebook account to shopify. along with joining another site to my shopify.
To verify and claim your domain with Google Merchant Center, follow the official steps here: https://support.google.com/merchants/answer/176793?hl=en
Or if you want a step by step guide: https://feedarmy.com/kb/verify-claim-website-shopify-in-google-merchant-center/