The Ball Joints MAY have plugs where you could install grease fittings. I did that on our 2002 Axle. That took the number of fittings up from Four to Eight. When adding Four to the Ball Joints, I chose some angled fittings to make it easier to get the grease gun onto them. Also replaced a few of the Four original ones (as shown on Bruce's excellent diagram) with angled.
Our 2012 Axle doesn't have Grease Fittings OR plugs on the Ball Joints. Sealed for Life? Ford meant it!