Exchange 2013 Mail Enable Existing Security Groups

Hello,

I can't seem to find how to mail enable an existing Security Group in Exchange 2013.  Does anyone know how to do this?  I have created them as Universal Security Groups in Active Directory.  I see that if you create them from the Exchange Admin Center, it will work, but I have a ton of groups with very complicated memberships that exist in AD and I would prefer not to delete them, recreate them, and adjust membership.

I looked for a cmdlet that would let me do this, but I can't seem to find one.

Does anyone know how to Mail Enable an Existing Group from Exchange 2013?

Thanks