Run javascript on top of Ember app

I'm writing a script that adds a tutorial on top of an Ember.js app. The problem is that the script is referencing elements that should be loaded by the Ember app. When the script runs, the elements are not yet loaded, even though the script is running onload.

How do I determine if Ember is done loading the page? I know the controller/template/component names, but I have no clue how to specify that the script should run AFTER their done loading.