Someone had just talked about this recently:
What I would do is unplug the return hose at the pump (it will create a mess or suck out as much as possible with a turket baster to minimize the mess), plug it at the pump reservoir and connect another clear hose to the return line out to a recovery bottle, refill the reservoir, start the engine, which will pump the old fluid out/new fluid in, stop the engine, refill again and get an assistant to start the engine and turn the wheel lock to lock as you refill the reservoir. Do this a couple of times until the fluid is clear. Reconnect the return line to the reservoir and refill it one last time. Turn lock to lock to ensure there is no air, check fluid level.