The Horsey Bank is your own personal bank that fills up with credits when you spin on a machine or complete a purchase. You can open the bank by clicking on the Horsey icon above the Spin button on any machine, or above the Collect Bonus button in any World.
Once opened, you can choose a new name for your Horsey.
The Horsey Bank starts our as "Locked" and will gradually fill up with credits. Once it's full, you will receive a special offer to claim all of the credits inside.
The Horsey Bank is being released gradually. You may not see this feature in your game yet, but it will be made available to more players over time.