The most common way or method to know how to use it is actually try it. Thanks for the Python interactive console, we can do that easily with auto-complete (Tab). And for most of the function, it will provide some basic information defined in function itself (basically a tooltip). Which will showed at autocomplete phase:
And for the rest of it, you might need to try it yourself to know how these collection, object, mesh, vector are stored(and link) in Blender. The you can roughly guess how you link a new object to a specified collection, by experience.
Also, there is some code snippet for handy function in Blender Manual as well. You might find something that you want or some workaround solution. Then you follow those code to help you complete your task.
Yes, it will be very frustrate to learn the structure in Blender and all other application. And if you are not familiar in "Python Class", you really should to learn about it at first. It should help you to understand Blender Python in every aspect.