Can you tell me how could I help my husband erectile dysfunction?

Find the cause. Medical causes need to be ruled out. In addition to the ones that everybody knows, hemochromatosis and prolactinoma need to be checked for. If he gets spontaneous erections while sleeping or during the day than when he is with you, full communication and being 'good, giving and game' is the key -- forego intercourse for a time and learn other ways to make each other happy until things normalize.