Just go into your gallery and use the share button, then select qooApps Photo Share.
Then the image will be transferred via Bluetooth to your Gear Fit2.
If the uploading to the Gear Fit2 fails, please unselect the Photo Fit Watch and then reselect it. A short toast message on the phone indicates a renewed connection. Then retry your upload again. The connection to the Fit2 may lost when phone enters lock screen and could not be reestablished afterwards.