I think you raise the gear lever - and the gear comes up! Worked last time I tried it in the sim (about 4 months ago).
But on the aircraft with the older RATS (min speed 140 knots - you can tell because CBs D02 and F 07 are yellow collared) the DC ESS BUS is on the batteries as is the AS ESS BUS through the static inverter, tou have to switch them back to the emergency generator by selecting EMER ELEC PWR to MAN ON.
This tells me that the gear is actually electricly powered by the DC ESS BUS - which makes sense if you think about it.