Calculate, how many grams of FeSO4 or FeSO4·6H2O you need for preparing this solution, then dissolve salt (or hydrate) in, say, about 300 ml of water, and after dissolution add more water enough to exactly 0.500 liter. Do all in 0.5 L volumetric flask.
This is a very bad teaching example since this salt is very unstable in water, and even as solid (eventually it should be stored under nitrogen or argon).