As a contest participant, you can change your own password through the password reset link at the contest site.
You will be taken to a screen asking for your email address. From there, a temporary password reset link will be sent to your email inbox.
You will need to click on the link in the email to set your new password.
NOTE: The temporary password reset link expires after 60 minutes. If you click the link after 60 minutes has lapsed, you will be taken to a screen to request a new password reset link.