How do I pair iOS Remote with iTunes?

I'm using iOS 10 on an iPhone 6, with the latest Remote app (updated today). I want to use it to control iTunes on my MacBook Pro, running OS 10.11.6. Both devices are on the same wi-fi network and have Bluetooth enabled. In the iOS Remote app, I click "Add a Device". It tells me to go to iTunes and click the Remote button in the top left of the window. But there's no such button! Where do I find it?