Click Recover Password.
Then, enter in the email address you use to log into iRacing and then click Submit.
This will send an email to that email address (make sure to check your spam and junk folders) which will contain a link to the password reset code website (http://members.iracing.com/membersite/resetpassword.jsp) and a password reset code (**THIS IS NOT A NEW PASSWORD**).
Go to that website (http://members.iracing.com/membersite/resetpassword.jsp) and enter:
1. Your email address (again)
2. The password reset code from the email you just received
3. What you want your new password to be
4. Confirm your new password
You should now be able to log into iRacing (members.iracing.com) with your email address and this newly reset password.