Hi, that pictured part slots into the front of the yolk assembly, just above the cablegroove for the wires below that part. This is a tricky job, I'd advice you put that part in the big groove between the black motor retainer and the vacuum housing. Then attach the yolk assembly and slide upwards to the part pictured. The wires slot into the yolk asembly groove.
The socket of the yolk assembly sits right at the front above the suction hole, just in front of the cleaner head stabilising lock (the Y shaped plastic bit designed to stop the machine falling sideways). This must sit flush into the front