For some reason I don't have an option to open this application on my N9. It said, "Installed" but "Open" button is greyed out. Any idea why? This is AT&T Variant.
I'm guessing it's not an app per-se (just like Good Lock 'apps' aren't really apps, just add-ons to Good Lock), so you can't open it and instead just adds functionality to the Camera app.
Sometime it happens with some non compatible apps.
You can install some other app for your device for the emoji usage.
Specially when there are so many free apps floating in the app store or otherwise.
If you want you can check out the list below. https://yourtopbest.com/top-best-emoji-apps/