Add the following code to the end of the URL after a space:
target="_blank"

The resulting code with the link would look something like this:
<a href="[URL]" target="_blank">[Link text]</a>

This can also be done for links using the built-in HTML editor by:
  1. Locate the text/link to edit.
  2. In the editor, click the Link icon
Link icon
  1. In the pop-up window, select Open Link in a New Window from the Target drop-down
Open link in new window
  1. Click Update