Hi @Eric Carr ,
if I got you right your VM is Azure AD joined and you want to install this VM as an additional domain controller (DC) to the Azure AD?
You can't promote a VM as an additional DC to the Azure AD. Azure AD is managed by Microsoft Azure and does not allow to add additional DCs.
If you want to create your own AD domain you can do that. But you have to choose Add a new forest
to install the first DC.
(If the reply was helpful please don't forget to upvote and/or accept as answer, thank you)
Regards
Andreas Baumgarten