Just say: Alexa, Turn ON device name or Alexa, Turn OFF device name to control IR devices with Nexus Home Ultimate Hub.
Note: Please make sure to give each device a unique name in the Nexus Home App so Alexa knows which devices you want to control. If you change the name of a device in the Nexus Home App, you’ll need to ask Alexa to discover devices to learn the new name of that device.