You created a VM named Host3 running Windows 11 and need to add it as a third session host to host pool Pool1. What should you do first?

To add a new session host to an Azure Virtual Desktop host pool, you must first generate a registration key. This key is used during the host agent installation on the new VM (Host3) to securely register it with the host pool (Pool1). Without a valid registration key, the VM cannot join the host pool. Assigning a scaling plan is for managing host power states and doesn't directly enable a new host to join. Generating a certificate for Host3 is not a required step for adding a session host to a host pool; Azure handles the necessary certificates for the AVD service. Deallocating existing session hosts would remove them from service and is irrelevant to adding a new one.