Login to your domain's admin interface. This is likely provided by whoever you bought the domain from.
Locate the page where you can set DNS records.
The page might be called something like DNS Management, Name Server Management, or Advanced Settings.
Create two records as follows (note the trailing periods):
ALIAS @ cloud.loft.hosting.
CNAME www my-domain.com.
Give some time to allow the changes to propagate the DNS network. It could take a couple minutes to a several hours.