FAQ: Working With Menus
How can I make a Menu Item point to an external web site?
If you want a Menu Item to link to an external web site, you need
to login, then either add a new Menu Item, or select and existing one
from under "Current Web Pages." Scroll down to the section labeled
"Menu Content/Action." You should see a box labeled "External Link."
Place the full URL in this box. Make sure all other boxes in this
section are blank.
Now, when someone clicks on your menu item, they will be taken to the
web site you specified.