How do you change the water filtration system filter on a whirlpool gold imperial series (ultra plus) refigera

Go to Whirlpool.com and enter your model number. You should be able to access an online how-to. If you're talking about changing a cartridge, it could be a very simple job to replace if it's showing through the grille at the bottom front. Just rotate it a quarter turn to the left (you might have to use pliers) and pull straight out. Don't be concerned about leakage, as there are o-rings. Then simply insert a new cartridge and turn one quarter clockwise. Then you have to bleed the air out of the system. Use a one or two quart container and fill it from your water dispenser. Done!