To set up your Sub-Domain, navigate to "Domain Hosting" in your Revmatics dashboard.

Type in the subdomain you would like to use(ex: shop.yoursite.com), scroll down and click "save".

After you have saved you will see a "TXT Name" and "TXT Value", these need to be added to your website's DNS records, just create a new TXT record, then copy and paste the name and value from our site.  

That may take a few hours to process(the DNS needs to propagate through the hosting systems), but when you come back to your Revmatics dashboard you will notice the TXT nave and value have changed. DO NOT replace the txt record in your DNS manager, just add a second record with the new name & value.

(The first TXT name should start with "_cf-custom-hostname", if that has changed to start with "_acme-challenge" then you are on the right track.

Once you have saved both TXT records, you just need to add a CNAME record with the value set to "landing.revmatics.ai"