I have no photos as mine is under a cover 150 miles away, but let me try to explain it.
There should be a sort of w shaped fitting on the fitting on the mast that the boom attaches to. That should be positioned so that the open ends of the "u" on either side face down before you attach the boom. To reef you lower the main and attach the cringle near the tack (assuming 1st reef) to the hook on either side, then tighten the halyard.
The "jiffy" part is what runs through the boom. The reefing line starts by being tied to the strap under the boom aft of the strap for the main sheet attachment (I forgot what those are called - sliding eye pads?). It goes up and through the cringle in the main near the clew, then down the other side of the sail. Then it goes into one of the three sheaves at the end of the boom (I don't know as it matters which - the other two are for the outhaul and the topping lift; I use my outhaul in the center sheave). If you know what lines are the outhaul and topping lift and have a 3rd that comes out the rear of the boom, use that. Then forward through the boom and out the corresponding jam cleat at the fore end of the boom. Once you tighten the halyard, you tighten that jiffy reefing line while up by the mast to pull the clew down and jam it in the cleat. Then use the lines in the sail to tie around the boom.
My sail has two reefing points, so if yours does you'd obviously have to move the jiffy reefing line between the two if you use the 2nd reef. I am on a lake and if the wind got to where I needed a 2nd reef I'd go in, so I just leave mine drooped through the lower (first) reef cringle.
By the way, I don't have a Kenyon - so the setup of the reef hook and pad eye on the boom may differ.