Pull off the seal that goes along the top of the engine bay, pull up the little cover over the wiper, then pull up the scuttle.
Reach into where the plug is (You will see two wires going down) then simply pull it out, removing it will mean all the fluids will leak out of the bottl onto the floor however as the pump also actas as the plug.
If swapping pumps over make sure you keep the current pump before replacement as you might need the rubber seal from your current one.