If you've lost your password, you can set a new password.

1. If you're currently signed in, sign out by clicking You → Sign Out
2. Click Sign Up or In
3. In the dialog that appears, click Sign In
4. Click Forgot Password?
5. Enter the email address associated with your account, then Reset Password
6. A password reset email will be sent to you. Follow the instructions in the email to set a new password.
7. Sign in with your new password