To change your password via the app:
Go to "Settings".
Click on "Security Settings".
Click on "Change Password".
Enter your current password and the new password in the designated boxes.
Click on "Change Password" to successfully change your password.
To change your password via the website, click on the blue profile icon at the top-right side of the page.
Click on "My profile".
Click on "Password".
Then follow the prompts mentioned above for the app.