To use the Samsung Gear VR (2016) with the Galaxy S6 Edge, you'll need to remove the headset's front cover by releasing the latches on both sides. Note the front cover is not actually used while the phone is installed in the headset. Its main purpose is to protect the headset lenses from dirt and dust when not in use.
Once the front cover is removed, you need to change the USB Type-C connector that is already installed on the headset to the micro-B connector.
To release the USB Type-C adapter, you need to place the switch on top of the adapter into an unlock position.
Once unlocked, you can pull out the USB Type-C adapter from the headset.
You can then push the USB Micro-B connector back into the slot to replace the USB Type-C connector.
You should also make sure the USB Micro-B connector is rotating up the connector, pushing down the rectangle button that you see in the A position, and then sliding the rectangle button from the A to the B position. This allows the Samsung Gear VR (2016) to connect to a smaller phone like the Galaxy S6 Edge.
You can then insert the Galaxy S6 Edge into the USB Micro-B connector.
The top part of the phone can then can latched on the other side of the headset.
Once the phone is connected over USB to the headset, the phone will automatically go into VR mode and open the Samsung VR App.