How can I access settings during development

Hi All,

I'm in the process of building my first watch app, and I have added configurable settings, in a settings.xml resources file with the following contents:

    <settings>
         <setting propertyKey="@Properties.api_key" title="@Strings.setting_api_key_title">
             <settingConfig type="alphaNumeric" required="true" />
         </setting>
    </settings>

Then I'm trying to access with

    var key = App.getApp().getProperty("api_key");

This all appears to be correct, but of course key is set to null because the setting hasn't been configured.

How can I access the settings on the device simulator?
File -> Edit persistent storage -> Edit Application.properties data returns a warning that the app has no settings. If I install it on my device, there is no settings button in Connect IQ.

Am I missing something?

Thanks in advance