Hi, welcome to GoY, start feeding them with half strength tomato fertilizer.about once a week, the leaves will die back naturally, but you will have fed the bulb for next year, I would leave the flower stem on the plant, and when it has died off will just pull out easily, if it doesn't pull out easily, leave it a bit longer, you can either take them out of their pots, and store them in dry sand, or you can leave them in the pots they're in, just let them dry off when they die back, next year you can start them off again, or plant them in the garden, if you pug them in the garden, plant them about 6 inches deep on a layer of grit, Derek.