If the glasses has a trigger button you can control it from there by pressing the button
If it's hands-free glasses you can control it with the device movement and a crosshair sign:
1. Place your phone device into VR glasses and wear it on your head
1. Move it to the right or left bottom with a head movement
2. The nine dot icon and a crosshair will appear on the screen
3. Move the green crosshair towards the nine dot icon to open control menu with a head movement
