Can someone tell me how to put this in order

By identifying the author, you are examining the origin in the source.

Explanation:

The main point of identifying the author of a text is to understand where that text came from, who "gave birth" to it, so to speak. In other words, we are identifying the text's origin. After doing so, we can move on to examining the others - bias, purpose, agenda. These points are dependent on the origin, on the author.