Open the Scratch website and click the Sign In link — this is where a user enters their password to log in to the Scratch website. At the bottom-right of the login menu is a "Need Help?" link, which directs you to a page where you can enter information to reset the forgotten password. Then there are two options: enter your username or enter the email address associated with it. Once the information is filled out, click the light-grey "Send me a password reset link!" button, which will automatically send an email in which you can reset your password. If you choose to enter your username, it will send the email to the linked email account, and vice versa.
If both the password and the e-mail account were lost, use Contact Us.