Yes...if the air file doesn't have these entries already, why not add them? If you borrow them from another model, you most likely will have to change the offsets (locations, in foot measurements) and the tank capacities to match your model's specs.
Offsets are measured left and right of the model's nose to tail centerline and above and below the lateral axis running through the wingspan. For most fighters, if the tanks are mounted between the cockpit and landing gear, its gonna be about 4.5 to 5 feet from centerline. Double that for tanks outside of the landing gear. Left locations are done with negative values like -5.00, so are locations below wing's lateral axis.