There are a few different ways that you can screen mirror with gear VR. The first way is to use the Samsung Gear VR app, which is available for free on the Google Play Store. Once you have installed the app, open it up and connect your phone to your gear VR headset. From there, you will be able to select what you would like to display on your phone's screen.
Another way to screen mirror with gear VR is through the Oculus app. This app is also available for free on the Google Play Store. Once you have installed the Oculus app, open it up and connect your phone to your gear VR headset. Then, select Cast from the menu at the top of the screen. From there, you will be able to choose what you would like to display on your phone's screen.
The last way to screen mirror with gear VR is through third-party apps such as AllCast or Miracast. These apps are not affiliated with Samsung or Oculus, but they do allow you to cast your phone's display onto your TV or monitor. Both of these apps are available for purchase on the Google Play Store.