Click the "Sign In or Register" button found at the top of the store:
Then click on "Forgot?":
Fill in your email associated with your store account, and submit.
A special email will then be sent to your email box. Look for it with 'Account recovery request' in the subject. Check your spam filters and folders if you do not immediately see the email.
The email will have special instructions on how to reset your password. Your password will NOT be changed unless you follow the instructions given to you in the email.
After you have completed the last steps, you will be signed in with your new password.
If you receive a recovery request email, it means someone else used your email address in the Forgot Form. Your account is still safe, and you can ignore the email (your password has not been affected).