LanCargo comprises several companies. ABSA in Brasil, MAS in Mexico, Florida West in Florida, I think Lan Colombia also has some freighters and Lan itself, which has the 2 B777F and maybe some other aircraft (not sure).
ABSA and MAS would imply to have the respective nationality. Therefore, if you don't have one of those nationalities, just forget it. For Florida West, I guess a Green Card would do the trick.
To apply for Lan, I guess you would have to apply via LanChile. Then again, don't know for sure.
Best of luck!!!