Very simple! You don't have to do anything for this. If a merchant approves the refund, the amount will be deposited via bonsai into the same account you paid with. Once approved, it will take a few business days for the amount to appear in your account as this also depends on how quickly your merchant's payment provider transfers the amount to Mastercard.
It is sometimes even possible that the refund will be deposited into your account BEFORE the original payment has been deducted. It will then seem as if we are taking the refund back from you, but don't worry, that is not the case. Your account had not yet been debited. If you do a little calculation you will quickly see that the net effect is 0, just like with any refund.