If you look at the back of the transfur case were the drive shaft goes in and you will see a plug on the side towards the bottom. That one is the drain plug, just above it a few inches is the fill plug.
There is no Transfer case oil. Just Transmission oil and that goes in the dipstick tube after the dipstick is removed. if its a standard there is a plug on the side of the tranny underneat fill to plug level