Use the Get component to retrieve information from the api; then process the data the Get downloads. 
Here is a tutorial showing one way to use the Wikipedia api; usually an api returns a json file that needs to be 'mined' for information.
This example may help you to understand the concepts. It is complicated and spends a lot of time discussing the Map component. Just read the content about using the api (you don't need the map parts to see how an api could be used to obtain information). A more simple example is Amazon Bookstore ; however the Amazon actual api is no longer available (this is an old tutorial).
What api are you interested in?