This article applies only to the Windows10 application.
You can only change the Password or PIN Code from inside the application. If you have forgotten your password and are unable to log in, please read the article: I forgot my password, how can I reset it?
Steps to take:
1 - Login to the Application
2 - Access the "Settings" option (represented by a sprocket) in the side menu.
3 - "Security" tab
4 - Enter the current Password/PIN Code
5 - Enter and confirm the new Password or PIN Code
6 - Click the "Change Password" or "Change PIN Code " button
You can see the whole process in this video: