You see here I remove the original connectors from the plug -
Fit them into the male part of the plugs you got yesterday -
Cut the repair wires to suit the length you want
Then you link a male and female repair wire with the 3rd wire which is the homemade loom you have. This pictures show crimps but these days I solder and heat shrink for neatness
Fix on the female connectors to one end of the repair wire -
Then you plug in the other end of the repair wire into the rear cluster in your case and connect the two black plugs.