Simply click the "I forgot my password" link on the login screen and follow the prompts.
You may also reset your password online here: http://talkchain.com/account
The system is entirely automated and the only way for it to work is if you've linked a valid email address to your account on your profile page. It is highly recommended that you add your email address there. If you don't include your email, you won't be able to use this system and are not guaranteed to get your account back so that's why it's recommended! For reference, your email will not show up anywhere in the app and we will never sell it.