How do I use the KEF Kube 2 w/ my Denon receiver?

I have a Denon receiver and 2 Infinity speakers. My stereo was set up some years ago (not by me) and I've never touched it because I know NOTHING about how it works.
My computer and my TV are hooked up through the receiver so I can enjoy music and movies through my speakers.

I just got 2 KEF speakers to add to the mix. I know how to attach them directly to the receiver but what do I do with the KEF Kube 102? What goes in the "in "and "out"? Where do I attach it to the receiver?
Please reply as if I know nothing about this type of thing, because I don't.