You miss this from colinc755:
"Once that is done, filling the transmission is not as simple as removing the top plastic cap. You must also remove the funnel that the cap rests in because Ford placed a piece of plastic in between the cap and the funnel, blocking any fluid that tries to enter. To remove this you must get a pair of needle-nose pliers and pinch in the snap ring and pull up on the assembly. This window that the pliers can fit in is incredibly tiny and removing this funnel will take a lot of patience. Once the funnel is removed, keep track of that plastic piece that sits inside it. You can now fill the transmission with fluid, I would recommend trying to match what came out and add .25qts-.5qts to it (this is because if you pour too little fluid you can't add anymore without removing everything you just removed). "