The way to change the power steering fluid as outlined by most pump manufactures is to jack and block both sides of the front axle, disconnect the return line, and then turn the steering wheel stop to stop with the engine off. After you get all the fluid you can then you start to fill the system in the same manner except now you want to keep adding fluid until the return is clean fluid, then replace the return line and continue untill you have no more fluid drop and no froth in the reservoir. Another good idea is to run some transtune in the power steering fluid before you go to drain it. Transtune is made by the same company as seafoam and designed for automatic transmission and other hydraulic systems.
93 f-150 xlt 5.0