As mentioned it's hard to take a photo of it. From up top, you'll see a plug in the area that I circled, but that's not the right one. The plug you want is even further down and out of sight, really.
Another tip is to not try looking for the plug as you reach in there. I was doing that at first, but it only limited my reach. Feeling for it would be better, and your head/face won't be in the way of your arm trying to reach for the plug.
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