I think your friend was trying to turn the crankshaft pulley, not the flywheel. Anyway…
Find the crankshaft pulley, it’s the big pulley at the bottom of all the belts, over on the passenger side of the car. It has one large bolt in the middle of it. Find the correct size socket and a large “breaker bar” and try to turn it either way. This shouldn’t take more force than an average guy has. If it will not turn, remove the serpentine belt and try again. If still no go, there’s a very small chance that something in the starter is bound up in the flywheel, but chances are that the engine is gone.