If you're looking to take part in a HydraVault, all you need to do is deposit some BUSD, and in return, you'll get USDy. The USDy will be minted by the protocol in accordance with the value of your BUSD deposit and the current price of USDy. There will be a 10% deposit fee that goes towards increasing the vaults Perpetual Ratio, which will be taken from the USDy the protocol mints.