To be certain, you should:
* Consult your owner's manual: This is the best resource for the exact location in your specific vehicle.
* Look for a rectangular black box with numerous connectors: The PCM is usually a fairly large, black plastic box with many wiring harnesses plugged into it.
* Check online forums and resources: Search for "1993 Ford F150 PCM location" on forums like Ford-trucks.com. You might find pictures from other owners that can help you pinpoint it.
Remember to disconnect the negative battery terminal before working near any electrical components.