The fluid is moving around and has a tendency to splash a bit giving changes in readings. If the level is low, fluid is added using a small funnel down the dipstick tube itself. It s very important to use the correct fluid for your particular vehicle and that information is likely both stamped on the Dipstick itself and printed in the owner s manual. The fluid should be a nice red or pink color, not brown or smell burnt. The fluid reservoir may be near the power steering pump, or may be located on the firewall and connected by a hose to the pump.
Many modern cars have a translucent plastic reservoir and the level can easily be observed.
Some cars have a small Dipstick built into the cap. The owner s manual should be consulted for the type of fluid required, but that information may also be printed on the reservoir.