Tin all your exposed wire ends, and ensure that your balance lead (that you cut off) has enough reach to get from the exposed wires on the DC plug to the fan power plug on your goggles –
Solder the red (+ve) wire from your case to one of the wires in your long cable, and the black (-ve) wire to the other.
On one side of the board, solder the +ve wire from the extended cable that we just connected to your case to the V in pad, and the other -ve wire to ground.
Also, like shown above, solder the +ve wire from your fan balance lead power cable to the V out pad, and the -ve to ground.