Bought a new url and I want to mask the subdomain url it's installed on

Hi everyone,

I bought a new url which I have redirected to a subdomain on my main website. I’d like to hide the fact that the new website is installed on a subdomain but I haven’t been able to find out how.
So https://www.new.com is redirected to my wordpress install on https://new.main.com and I’d like the url to show as https://www.new.com

Can someone please help me out?

Kind regards,
Amanda