Navigate to Burp Suite > Comms (Free version) or Burp Suite > Options (Pro version) and scroll down to x509 certificates.
Highlight and click any of the certificates you wish to view and the following pop-up screen will appear:
Okay so that is it. Shows a whole bunch of information on the certificate. Not much too it but I've found that some folks didn't know about this feature so I figured it would be worth mentioning.