To change your password, you’ll first need to log out of your account. Once you're logged out, click on “Log in” in the top right corner of the page. When the login popup appears, click on the “Forgot Password” link. From here type in the email address associated with your account. You will receive a password reset email within a few minutes. Click the link in the email, which will prompt you to create a new password. 

If you created your account via Facebook, you cannot reset your password. Your login credentials are 100% tied to Facebook.