Here's how to open the various types of links on the site in a new tab. 


Buttons


Add new=true to the button shortcode, for example:



Text Links

In the visual editor, click the link, then click the pencil icon to edit. 




Click the gear icon to open Link Options. 




Check the box next to "Open link in new tab"




URL Fields


Click the button to select a new link.


Or click the pencil icon to edit an existing link. 



Check the box next to "Open link in new tab"



Hit Update to save the link, then Update again to save changes to the page.