Href prefix settings

Hi everyone, I created a website with Webflow for a client. He would like to publish this site as a subpage under his own domain (ClientName.com is for sale | HugeDomains). I have read that an href-prefix has to be set. Do I only have to enter the subpage under “Custom Code - Advance Settings” or do I have to enter something under “Hosting” as well. What entries does the customer have to make?

Thank you in advance for your help!