This item will give you one use of the /frostwalker command - it allows you to put the Frost Walker ability on boots (you can buy multiple uses for multiple items).
To give your boots the Frost Walker ability, simply hold them in your hand and use /frostwalker
Frost Walker ability details:
If you ever wish to remove the Frost Walker ability from a pair of boots, use /frostwalker remove - you will not get any extra uses when you use this command.
You can also toggle the ability using /settings FROST_WALKER.