if you do have the service book on this truck then yes the setting pressures and locations where to check should be in there.

usually the steering pressure operates off the secondary circuit in the hydraulic system which is also the auxiliary pressure for the hydraulic system. They use a priority valve to regulate how the pressure is distributed to each of the systems (aux functions and steering).
At least in most of the newer designed lift trucks I've seen it done this way. Some older trucks did have a separate steering pump but they eventually got away from this design to eliminate the extra pump driven off the motor to reduce drag on the motor. If by chance this has the steer pump then the pressure would be set directly on the pump via a relief valve.

But i think you'll find this unit has the steering relief pressure controlled by the hydraulic auxiliary circuit.