2002 Ford Explorer A/C clutch does not activate

There are literally dozens of things that will prevent the clutch from engaging, the most common of which is simply low refrigerant. That's not actually as simple as it sounds because it indicates a leak that can get very expensive.
Your first step is to put a set of professional gauges on it and determine if it has sufficient pressure to engage.
If it does, then your going to need a wiring diagram and the tools and knowledge to troubleshoot the circuit.