Do some research on L-Citrulline, since it is a precursor of L-arginine and allows higher amounts of arginine to be used by the body when compared to taking arginine supplements.
The most pleasant way of consuming L-citrulline is to eat a large slice of watermelon, making sure to eat the white coloured flesh part which contains the most of it. If you find yellow skinned watermelons, they contain the highest amounts.
L-citrulline is a precursor of nitric-oxide which is what dilates the blood vessels in the penis, that's why watermelon is often nicknamed nature's viagra.