Hi and Welcome. I'm Joel and I look forward to assisting you today with your question.
I've had a quick look at the cable you had installed from here
I don't see one with 1xred/1xblack and then 2 smaller black cables? The 16/2 cable should only have a black and a red.
In any case, don't worry about the 2 smaller black wires or if the cable has a white and a green, ignore them and snip them off. What you are interested in is the negative (black) and positive (red). So to hook them up, make sure the red is connected to the + post on your speaker and black is connected to the - post on your speaker binding terminals. Not sure what speakers you have but some you just insert with the clamp mechanism while other you loosen the screw - insert the bare wire and then tighten down the screw.
Same goes for your receiver, strip the end of the cable, cut off the 2 smaller black wires so your just left with the large red and large black wires. Strip them to bare wire and twist the wire strands to make a point of bare wire. You want to unscrew the terminal on the Denon which corresponds to the speaker, for example, Front Left, unscrew the red positive, insert your bare red wire then tighten, repeat for the black negative cable. Thats one done, then repeat for all speakers, Front Right etc