There are 11 obtainable items in Secret of Mana. For most of the items, you are allowed to carry up to four of each. The exceptions are Moogle Belt, Midge Mallet, Flammie Drum, and Magic Rope; these four items are only obtainable once, but you can use them as many times as you need to throughout the course of the game.
Items are usable through the game's ring menu, accessed by pressing the button (or button for CPU-controlled characters). Select the item you want with the button. Items cannot be used during cut-scenes and when your character is in the middle of casting a magic spell. If you cannot use a particular item at a certain time, you will not be able to choose it (for example, you cannot use the Flammie Drum while indoors, or you cannot use a Cup of Wishes when all of your party is alive). Click on an item to the right to get a detailed description.
Cup of Wishes
Midge Mallet will inflict or cure shrunken status ailment to a member of your party. Unlimited use. Return to Gaia's Navel just before you leave for the Upper Land and speak with the dwarf by the door to the Earth Palace to get it.
Moogle Belt will inflict or cure moogle status ailment to a member of your party. Unlimited use. Visit Sea Turtle Island in the sea west of Matango to get a Sea Hare's Tail. Take the tail to Kakkara and give it to the king to refill the spring. He will give you the Belt.