If you have created ACL enabled app, then CreateTimer/CreateGame method can only be done by admin and not by the end user. That is the reason, you need to pass admin key to call this method.
I dont think you need to call this method inside your app as you probably don’t need dynamic timer creation from the app.
We are working on to have creation of timer from AppHQ console itself for administrative purpose.
Let me know if it helps.