Facebook profile picture is your "face" on Facebook. It help people know you when someone have same name with you. You can change profile picture whenever you want. Now, following this introduction, How Facebook will help you change your Facebook profile picture.
First, you login to Facebook:
Next, go to your Facebook Timeline, you can click here and go to quickly
Then, click Upload Profile Picture:
Next, choose one of your photos or upload a new one, here I upload new photo ~> +Upload Photo:
And, select your picture you want to upload:
After that, Drag to Reposition this picture and Save:
Done.