Your options are limited and carry varying degrees of risk and success:
* Dealership/Professional Mechanic: This is the safest and most reliable option. A mechanic might have access to diagnostic tools that allow them to reprogram the vehicle's computer to disable the chime, but it's not guaranteed. They might also identify the underlying cause of a persistent chime (a faulty sensor, for example), instead of simply silencing it. Expect to pay for their time and expertise.
* Aftermarket Solutions (Use with Caution): Some aftermarket devices or harnesses claim to be able to disable various warning chimes, including the key-in-ignition one. However, these are not officially supported by Ford, and improperly installing them could damage your vehicle's electrical system or void your warranty. Research any such device thoroughly before attempting installation, and understand the risks involved.
* Pulling the Fuse (Not Recommended): While you might be able to find the fuse for the chime and remove it, this is generally not recommended. Pulling a fuse might disable other important functions beyond just the chime, and it could potentially be harmful to your vehicle.
Before trying any of these, consider WHY the chime is activating. It's designed to alert you to a potentially dangerous situation – leaving the key in the ignition. If the chime is going off frequently despite the key being removed, there may be a problem with the ignition system or a related sensor that needs professional attention. Simply silencing the chime doesn't address the underlying issue.
In short, taking it to a mechanic is your best bet for safely addressing this. Trying other methods carries significant risk.