API Help

My boss wants me to use an API to pull cambium radio data out of CnMaestro.  I'm new to the IT world so API is a new concept for me.  I have found a few pages on THWACK regarding API but they all seem to be structured under the assumption that you already know how the system works.  Is there any place I can go to learn about using API?  specifically where I enter API commands and how I reference an outside server?