That dialog is for JavaScript scope, not TypeScript scope (e.g. see mocha demo http://youtu.be/4mKiGkokyx8?t=1m19s). That is, Webstorm is using TypeScript definitions to give intellisence for JavaScript.
For TypeScript itself you need to include the definitions into your project manually (https://github.com/borisyankov/DefinitelyTyped/blob/master/angularjs/angular.d.ts) and reference them like you always have.