How do I add an AVCaptureConnection to an existing AVCaptureSession?

Im trying to build a camera based off of Apples Using AVFoundation to Capture Images and Movies. I would like to add an AVCaptureConnection to the existing AVCaptureSession so that I can edit the isVideoMirroring property. However I am not sure how to go about adding an AVCaptureConnection into the code. Thank you for your help.