How to add how did you hear about us to the email notication shop owner receives

[mlotorocks]

I need to add a how did you hear about us field to the email that the shop owner receives.

I have added the dropdown to the cart by following a tutorial but none I've found have shown how to add that to the email notification.

Additional I saw that this information should be viewable in the order itself under Additional Details but that area is not in the order. Can someone point me in the right direction, thanks in advance!