Trouble with Ember project - filling a text-field based on selection

I've never worked with Ember, and am fairly new to JavaScript, and have for the past couple of days been trying to translate my HTML and JS into the Ember framework (I got some help from a friend). The first feature of the project should simply be able to fill a text-field with longitude/latitude of an inputted address. The second feature of my project is based on a selection from a drop-down menu (drop-down is made of different counties), and fill another text-field with a specific email address depending on which selection was made.

The problem I'm having: I can't seem to figure out how to fire up my setEmail function as I need it to recognize a value (1, 2, 3, 4 etc.) from the selected county from the drop-down, and based on that value; fill in the text-field with the correct email address. I've heard about Ember Observers, but cannot seem to figure out how to implement them for the drop-down I built. I'd really appreciate if someone could take a look at my project and give me pointers on what I could improve, or even do completely differently.

Here is a link to an Ember Twiddle of my project: GeoApp

I appreciate any suggestions and insight! Thank you.