Prior to resetting you password, make sure that the new password is for your FX+ account and not your cable provider's account.
To reset your password go to the FX+ Homepage and select Sign-In
Then on the sign-in screen, simply click where it reads "Forgot Password?"
From there, you will be taken to a screen where you can put in your email to reset your password. Once you've provided your email, you will receive an email from email@example.com
Open the email and click on the "Reset Password" button. From there you will be taken to the Reset password page where you enter in your new password and confirm it then click "Save Changes".
After this, you should be able to log-in to your FX+ account with your new password.