Take a look at this project, it’s a starter app created by Ionic:
It’s a working demo that demonstrates several of the things you’re asking about, including consuming an API.
Everything you build in Ionic will need to be written in java script. Ideally your Yii web service should provide data in JSON. You’ll want to look at the file “src/providers/api/api.ts.” It’s a simple class written in java script that can consume a remote web service. It offers methods for get, post, put, delete, and patch.