How do I edit cfg file for payload?

[michaelb15]

Im trying to add payload sections to the c 130, because it doesnt have anything in the payload section. Not even for pilots, so when I fly it the only weight it has is fuel, with no way to add any kind of payload. even with full fuel there is still room for 25, 000 lbs of cargo, which I would like to fill 

[garymbuska]

Not sure if you really want to do that as you can always adjust both fuel and cargo by clicking on the change fuel payload section after selecting a aircraft. but if you do then this is where you would make the change
[WEIGHT_AND_BALANCE]
max_gross_weight = 20450.0