sub domain test url instead of domain name

Hi All

I have just built a site on my zen hosting for a client. My Zen set it up on a sub domain first and then when you’re happy with the site you can then push it up to the domain name.

The problem I have is that now the site has the sub domain url rather than the new domain even the tho the new domain takes you there, when you click on a mwnu tab it has the sub domain name in the url.

Do I need to change the htaccess file?

Thanks in advance

Kai