Ask HN: How do I build apps with APIs?

This is the one part of Web Development so far that has me completely stumped me.

For example I go to the API section of a site. I see the url that I need to use and the parameters. I play around with it a bit in my address bar and I get the data I want. Great! But how do I take this information and build something out of it then render in html/css?

I have tried looking up tutorials and things but there seems to many different ways to go about this and it confuses me even more.