Here's what you should do:
* Check all possible locations: Thoroughly search your home, car, and anywhere you might have misplaced the key. Look under seats, in drawers, and even in unlikely spots.
* Spare Key?: Do you have a spare key? This is the easiest solution.
* Ford Dealership or Locksmith: This is your best bet. A Ford dealership, or a locksmith specializing in automotive keys, should be able to create a new key for your car. They will likely need some form of vehicle identification (VIN number) and possibly proof of ownership. Expect this to be relatively inexpensive for a 1993 model, compared to newer vehicles with advanced immobilizer systems. They may need to look at the ignition lock cylinder to determine the correct key blank.
* Avoid DIY solutions: Attempting to bypass the ignition system or make your own key is risky and could damage your car or even be illegal.
Important Note: The 1993 Ford Fiesta LX likely doesn't have a transponder chip in the key like many later vehicles. This simplifies the key replacement process considerably. If you have trouble finding a local locksmith experienced with older vehicles, explain this lack of a transponder system. It makes the job much simpler and faster.