Once this option is selected, two links will appear to the right of your menu editor:

Edit and Add external link 

By selecting Edit a window will pop up with a list of all the links that will be displayed in your navigation menu.

 

You can edit the text of these links by clicking on their names, or to hide them you can click on the switch to the left. 

The Show albums switch will also display direct links to any or all of your albums in your navigation menu.

 

 By selecting Add external link you can label and enter the URL of any link you like and this will be displayed in your navigation menu.