If you do not remember your current password, please check out:
How to reset my password? I forgot it.

Otherwise, changing the password is straight forward:

• Open RatingWidget’s management dashboard:
  http://app.rating-widget.com/
• Sign-in with your email and current password
• Click the Account Settings
• Enter your current password
• Type your new password twice to make sure there’s no mistakes
• Save by clicking Update Account Details