I need to change the power steering fluid in my BMW X5

Here is your answer that should help. I personally do not care why you want to don this, it is your business, if you wanted my opinion on that, I feel you would of asked. Here is the answer you wanted however.
Hello Sir. Usually it would say in the owners Hand book you got with car? explaining all the controls functions of the car or 4x4? alternatively if you look under bonnet there only be four filling reservoirs: engine coolant water, washer bottle, brake Fluid,power steering. usually the engine coolant will be a largish cap about 2-3 ins either blue or black its NOT this one. The brake fluid Will be at the back of engine bay and so NOT his one. Washer bottle again will be a cap blue in color its NOT this one. the one you want should be near front of car /engine and should have a steering wheel symbol on it the caps usually smaller then the engine coolant and black attached to a small reservoir and when you remove it will have a dipstick attached to it or small spike attached to cap this is used to measure power steering fluid, hope this helps... Thanks Mike

Can you tell me why you need to change the power steering fluid? I've never heard of doing this and the maintenance schedule in the data base that I use doesn't call for changing it.