Enter in the email address you used when you setup your Bookshelf account.
You will recieve an email that has a link in it. Click on the link and you will be taken into your profile page. (Note: This link is only valid for 24 hours and once it has been used it cannot be used again.)
Once you are logged into your profile page change your password and re-enter the new password in the confirmation field.
Once you’ve updated your password click the save button to save your new password.