Select your image and choose the "share" button. Then choose "device" to save your snapshot to your device. Once you have this saved you can share your image however you like from your devices images.
You should always save any snaps you wish to keep to your device, as these are unique to your game and not retained if you need to reinstall/reset/change device.
Currently it is not possible to share directly from Splash and images can only be saved.