If you already have a Games With Friends account and you have NOT yet set a password you will need to set one:
Alternatively, if you have the original device your account was created on you may use the following instructions:
Launch Chess With Friends on the old device where you created the account (iPhone, iPod touch, iPad).
Tap on the "Settings" button.
Create a new password.
Tap "Save and Close."
Launch Chess With Friends on your new device and login with your new password.