Ask HN: Where/how do I learn very basic API skills?

I am learning to build software since this January. Now I know the very basics of CSS+HTML, some Javascript and C#/.NET. Enough to create from scratch, publish and sell a very simple SaaS (in my case, the first "S" could stand for "spreadsheet", so simple is my service). I learned with Codecademy, Treehouse and try and error with the enormous aid of Stack Overflow. But now I want to create a very simple site using a API. And I can't find the right place to learn it. I mean, even Codecademy have this thread, but everywhere all API learning resources look aimed at more advanced developers. There is no basic tutorial on how to do it. I mean, very, very basic tutorial, telling me how to establish the connection, where to write my code with the GET/POST/PUT/DELETE, what the hell RESTful means and if this is something relevant to my basic code or just a theoretical base if you to go further down the road. So I wonder, do I have to be a proper javascript developer to even start learning API? I am not a proper C#/.NET for sure, and still could build a simple logic with try and error. I guessed I could do the same with API, am I wrong? PS: I already have a project in mind, I want to build a tool using the API of HNSearch: https://www.hnsearch.com/api So I want to learn generic API development, not a specific one.