Take a look at this article which provides the steps for preparing your environment to back up a Resource Manager-deployed virtual machine (VM). The steps shown in the procedures use the Azure portal.
The Azure Backup service has two types of vaults (back up vaults and recovery services vaults) for protecting your VMs. A backup vault protects VMs deployed using the Classic deployment model. A recovery services vault protects ** both Classic-deployed or Resource Manager-deployed VMs** . You must use a Recovery Services vault to protect a Resource Manager-deployed VM.