Navigate to the Settings-tab.
Mobile device: Hit 'More' on the bottom right corner, then press 'Settings' from the pop-up menu.
Computer: Click 'Settings' from the list on the left side of your browser window.
The button to change password is on the very top of the menu.
Provide your old password and fill in your new password twice.
Press 'Save' and voilá! You will receive a notification on your screen that your password has been changed.