What is the process I need to take to get off of my fentenayl patch-50mcgs every 48 hrs for the past four yrs?

Gradual tapering . Your doctor should guide you and provide necessary prescriptions. Usually it goes as following: starting fentanyl patch 25 for a week, then 12.5 for the second week. Then either stop completely or continue the process taking decreasing doses of oral medication such as vicodin or oxycodone.
Taper. First I do wish you well in your decision to reduce use of opiate pain medication. Talk with your primary care or pain management physician to make a tapering plan. Do not try without medical assistance. Besides tapering the fentanyl patch dosing and/or frequency, other medications may be used to help with pain or withdrawal and may include oral opiates or antidepressants which could both help.