Publish your campaigns connected to your own sub domain
First connect your domain following the guide here
Once you have set up your campaign, and click 'publish campaign' - or navigate from the action tab in the dashboard.
You will see on the right a 'Connected sub domain' under the publish section. Click it.
If set up correctly you will see the following prompt where you can access your campaign URL.
If it was incorrect in your CNAME set up, you will see the following prompt. Go back and reconnect your sub domain.