Using a licensed open source code/library

Currently, I'm working on a Device-to-Device transfer project named Share, as a part of a project I've used some of the code in share and modified some of it so that it can be used in it. And the project from which I referred the files is licensed under Apache License 2.0. I didn't understand the license doc completely. I used that code and did some modifications.
So what things we should take care when we use licensed code?

@yanokwa helped me in understanding few things

As ODK is Apache Licensed, we can use any Apache Licensed code or library. And if some file is changed/modified and a project is Apache Licensed then there is no need to add some documentation related to the modifications or the changes that has been done in the file.

But its always nice to include or mention about the project or the developer whose code is used.

Please add some suggestions or correct me if I misunderstood something.


I think that is a pretty good summary!