If you're unable to sign into your account, and have checked that you are using the correct email address, and have verified your email address (you'll be prompted if you need to do this), you may wish to reset your password.
You can do this by clicking the "Forgot your password?" link as shown:
Enter your account email address and a password reset email will be sent to you immediately:
When you receive the email, click the link and enter a new password as prompted.