I would like to use the Gauntlets of Ogre Power, which states that the item "requires attunement".
What am I supposed to attune it with?
What are the requisites/requirements?
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You can read up on attunement in the freely available basic rules.
Here are a few of the most relevant excerpts:
Some magic items require a creature to form a bond with them before their magical properties can be used. This bond is called attunement[...]
Without becoming attuned to an item that requires attunement, a creature gains only its nonmagical benefits, unless its description states otherwise.
So, you can wear them as normal gauntlets fine without attuning - but you you won't get boosted strength until you do attune to them.
Attuning to an item requires a creature to spend a short rest focused on only that item while being in physical contact with it[...]
So when you ask 'What am I supposed to attune it with?', the answer is that nothing extra is needed - just you, your item and and bit of quality time.
An item can be attuned to only one creature at a time, and a creature can be attuned to no more than three magic items at a time.
Attunement prevents one character having too many powerful magic items - as any given character cannot attune to more than three at a time.
Some items do have prerequisites - the gauntlets do not.
The gauntlets' rules text states 'Wondrous item, uncommon (requires attunement)'. So they don't require any prerequisite, beyond having a free attunement slot - and even if you don't have an empty slot you can simply un-attune to one of your previously attuned items and free the slot up for the gauntlets.
An item that did have a prerequisite, such as a Pearl of Power, would state that requirement explicitly. For instance, the Pearl's rules text states 'Wondrous item, uncommon (requires attunement by a spellcaster)'.
That said, wearable items do have a sort of hidden prerequisite, unrelated to attunement - they must be worn as intended:
Using a magic item's properties might mean wearing or wielding it. A magic item meant to be worn must be donned in the intended fashion: boots go on the feet, gloves on the hands, hats and helmets on the head, and rings on the finger. Magic armor must be donned, a shield strapped to the arm, a cloak fastened about the shoulders. A weapon must be held.
That means that someone without hands could not use the Gauntlets of Ogre Power. You wouldn't gain the benefit, if for instance, you wore them, somewhat clumsily, on a string round your neck. Sadly even a one armed character would be unable to use them - they must always be worn in a pair.