To view your 360° photos with Samsung (Oculus) GearVR you have to download the 8k equirectangular file from your cloud account. You find a download link under each of your 360° photo.
Open the desired 360° photo and click on which will open up a menu.
Note that you have to download the 8k version, because the 16k version is not yet supported by both devices.
After downloading the file, you have to put the file onto the mobile device you are using for your GearVR headset. The default directory to put the file in is "Computer\Galaxy S6\Phone\Oculus\360Photos".
After putting on your GearVR, your 360° photo will appear in the 360° Photos menu.
For additonal information and Oculus support, please follow this link: https://support.oculus.com/help/oculus/866319816819547?helpref=uf_permalink