How to access data from a JSON API ?

I'm trying to use the New York City Bus API in order to create an app. The last API I worked with, was while learning Python. I have no idea where to begin.

This is the link to the documentation http://ift.tt/2mMz9Yq

If you guys could point me towards how I can get the data from the API. I already got the Key.

Thank You so Much