trying to set a parked domain as main url and it's not working

Hi there,

I am trying to launch a new wordpress site with a parked domain as the site url. The thing is I already have a wordpress site with this parked domain as it’s site url. So what I did was go into the old site at root/wordpress/ and then just give it the site url of root/wordpress/. I then logged in to the new site and gave it the site url of mysite.co.uk with the wordpress url of root/test_site/. I thought that this would then just change my new site’s url to the parked domain of mysite.co.uk. but the old site is still there. Can anyone let me know as to what I might have done wrong and any help would be much appreciated?

Thanks,
Olly