The 5.7.2 Version of Concrete5 does not give us the option to make a link open in a new tab. Concrete5 staff have said, in their discussion forum (read the discussion), that they plan to add this functionality in the next release. But, for now, the way to configure your links so that they will open in a new tab is to edit the HTML directly.
First, click on the source code button:
Next, find the link you would like configure:
Then, edit the anchor tag, inserting the attribute target=”_blank”:
<a href=”http://clear.msu.edu/clear/” target=”_blank”>here</a>