Link at the bottom of the page

Hi,

probably a studpid question, sorry!!! But I'm trying to find out, how to place a link at the bottom of my site (in the menu at the end of the site).

But I want that link ONLY there, not in the menu thats at the top of the site.

And I also would like to know if it is possible, to have a link in a menu link to an external site?

Thank you so much in advance for your valuable help!!!