The strings for any emails that JFBConnect sends should be found in our language files. Look in /languages/en-GB/en-GB.com_jfbconnect.ini (or other appropriate locale for a different language), and look for the following keys to edit:
COM_JFBCONNECT_EMAIL_REGISTERED_BODY
COM_JFBCONNECT_EMAIL_REGISTERED_BODY_NOPASSWORD
COM_JFBCONNECT_EMAIL_REGISTERED_WITH_ACTIVATION_BODY
COM_JFBCONNECT_EMAIL_REGISTERED_WITH_ACTIVATION_BODY_NOPASSWORD
COM_JFBCONNECT_EMAIL_REGISTERED_WITH_ADMIN_ACTIVATION_BODY
COM_JFBCONNECT_EMAIL_REGISTERED_WITH_ADMIN_ACTIVATION_BODY_NOPASSWORD
This should be all that you need to do, so let me know if you run into any issues.
Thanks
-Melissa