Configuring Realm for AD

I am trying to figure out how to provision CentOS 7 hosts and have them automatically join AD after creation. I can configure CentOS 7 puppet module to install the necessary packages and the ‘realm join’ command supports getting a one time password. From what I read, Foreman can provide that one time password, but I don’t quite understand how to set this up even after reading official documentation. When I try to create the realm, it’s asking for a realm proxy, which is empty. How exactly do I do this?