It's not something that you can easily do without excess to a lift and the correct diagnostic tool, since the ATF temperature has to be monitored during the process, but here is what's in the Ford shop manual :
Check Transmission Fluid Level: CAUTION: The vehicle should not be driven if the transmission fluid level is low as internal failure could result.
CAUTION: The transmission fluid fill plug is located near the exhaust system. The exhaust will be extremely hot during this procedure.
NOTE: If the vehicle has been operated for an extended period at high highway speeds, in city traffic, during hot weather or while pulling a trailer, the transmission fluid must cool down to obtain an accurate reading.
NOTE: If the transmission starts to slip, shifts slowly or shows signs of transmission fluid leaking, the transmission fluid level should be checked.
NOTE: Do not overfill the transmission. The transmission fluid level must be at the upper level of the crosshatch mark.
NOTE: If the installation of a new transmission fluid cooler, cooler tubes have been carried out the vehicle must be driven to get the transmission fluid to a temperature of 88°C (190°F) in order to purge the air from the transmission fluid cooling system.
1. With the engine running, place the transmission selector lever in each gear position and hold approximately 5 seconds. Place the transmission selector lever in PARK. 2. With the engine idling (600-750 rpm) in PARK, position it on a hoist. For additional information, refer to Maintenance/Service and Repair. 3. Remove the transmission fluid fill plug transmission fluid level indicator assembly, located on the passenger side front portion of the transmission case. 4. Separate the transmission fluid level indicator from the transmission fluid fill plug. 5. Wipe the transmission fluid level indicator clean. Reinstall the transmission fluid level indicator only back into the transmission fluid fill plug hole to check the transmission fluid level. 6. Using the scan tool, verify that the transmission fluid temperature is between 80°C-85°C (175°F-185°F). Do not overfill the transmission. The transmission fluid level must be at the upper level of the crosshatch mark. 7. NOTE: If the transmission fluid is not at the correct level, follow the steps for Adding Additional Transmission Fluid or Removing Transmission Fluid. For additional information, refer to Transmission Fluid Drain and Refill. Install the transmission fluid fill plug. * Tighten to 35 Nm (26 lb-ft).