Redirecting domain to multisite URL

We launched our first Sitefinity site in June for dawnfoods.com. When we launched this site we did a DNS change for the existing site (same URL) to point to the new site. We are now launching our first SF 'multisite' with the URL of dawnfoods.com/uk. The site URL we want to redirect to this new site is dawnfoods.co.uk. A DNS change didn't work in this case. Where in Sitefinity do we need to set this redirect?

Thank you in advance for any assistance.