Truck Repair: air conditioner recharging, ford f350, power stroke

Question
I have a 97 Ford F350 and I am needing to add refrigerant to my system. Some one told me to put it in the high side but i just saw your answer about putting it in the low side. Can you tell me where it is located on this truck it is a 7.3 diesel power stroke. I have spotted the nozzel at the holding tank but it is black where can I find it and where is it located.

Answer
The charging port location varies based on the year of the truck --- on a 1997 truck the low side port is located on or near the accumulator / drier.  I am assuming that the tank you are refering to is the drier --- the nozzle is the charging port.