external link in nav bar?

Hi Tom,

Thanks for a fabulous theme, as always! I would liket o link to a sub-domain in the navigation bar. How do I do this?

This is the site so far:
http://jerusalemchallahcenter.com/

I want to have a nav bar item "shop" and link to: shop.jerusalemchallahcenter.com

And also a nav bar item ""home bakers" or something like that, not sure how to word it at the moment. It would link to: atasteofchallah.com

Is there a way to do this, to add links to outsides sites within the nav bar itself?

Thanks for your help,
Dina