Because the exact placement can vary slightly depending on the year and specific model of your F-150, the best approach is to consult your vehicle's repair manual or a wiring diagram. These resources will show the exact location of the IAT sensor for your specific year and model. You can also search online for diagrams specific to your year and engine. Searching for "[Your Year] Ford F-150 5.4L IAT Sensor Location" should yield useful images.
Remember to be careful when inspecting or replacing the sensor, as the intake system can be sensitive and components can be fragile.