Hi Tracy,
You cannot add a domain account under a Windows Resource. PMP handles passwords based on its exact source. So you should have one WindowsDomain resource under which you can store all your domain accounts and manage them. The Windows resources should only have local accounts under them.
You can try the steps posted by Rickie in this thread. It will automatically fetch all the Windows Box and also add the DC for you with all the service accounts automatically discovered and listed under the DC resource.