If I understand your question correctly...
The RAT is a "Wind Powered Hydraulic Pump", much like a Wind-Turbine, but in this case attached to the belly of the aircraft.
That pump, powers the Blue Hydraulic System, just like the electric motor normally would. Most hydaulic pumps require some sort of motor - electric, engine driven (accessory case), etc - to power a Hydraulic pump . In this case, it's basically the free spining propellor of the RAT that powers the pump.
Next, an Electrical generator is powered by the Blue Hydaulic system.
Was this what you were looking for? Let me know if you would like me to email you that section of the FCOM or AMM.
Cheers