It's not easily accessible without removing components, and its exact location can vary slightly depending on specific configurations. You'll likely need a repair manual or a detailed diagram specific to your truck's year and engine to pinpoint it precisely. Searching online for "2006 Ford F-250 6.0L Powerstroke Exhaust Pressure Sensor location" with images will be helpful.
Keep in mind that working on the exhaust system of a diesel truck can be dangerous due to high temperatures and pressure. If you are not experienced working on vehicles, it's best to consult a qualified mechanic.