Azure Active Directory Domain Services + Azure Multi-Factor Authentication (MFA) ??

Hi!

my scenario:

“Azure Active Directory Domain Services” is ready setup in Azure. A VM is added to Azure and added to the Azure AD. On this VM is running a website on IIS that is public facing (443). User can logon to this with his Azure AD user accounts. All user has “Azure Multi-Factor Authentication” (MFA) enabled in Azure.
Now: How I can configure the IIS site to use “Azure Multi-Factor Authentication”?

Regards,

Pawel