To interact with a vault you'll need to first approve the vault to spend the underlying on your behalf. Let's say you want to supply some DAI on the related Morpho-Aave Dai Supply Vault: first, you'll approve this vault to spend the amount wanted. Second, you can use one of the two functions available to supply tokens (knowing
mint depending on your will). You'll receive the corresponding token
maDAI on your contract or wallet. Its value increases over time while interests are accrued through Morpho-Aave.