To add a link to an external page (for example, a 'Contact Me' email link),click the "+" Add content icon on the left hand column of your Portfolio editor or the "+" icon in the lower right corner of your Manage Content menu.
From there, click on Link.
Type in the title of the new link:
Note: the format for this link in your Navigation bar to directly send an email to you is:
mailto:[YourEmail] -- no spaces!
The external page or direct email link will be located under Manage Content in case you'd like to edit this in the future.
*Please note—if after these steps your mailto link is still not working:
1) Make sure that your mail client is set to allow mailto links.
2) If the mailto link is set to open in the current window vs a new tab (via the checkbox in the link dialog), it will mostly just show a blank white page when the link is clicked on in preview. The link should work everywhere else though, including the published site.