You could automatically send a message to your newly added delegate.
Once you've set up delegate access, Outlook would offer to send a message to your delegate with news of these permissions. If you chose not to send this message when it is offered, you would need to make sure later that your delegate was aware of being a delegate.
Note There's more to delegate access than just getting someone else's meeting requests. After you have Outlook send the notification, you may want to send another message suggesting that your delegate take this course to learn more.