self sign up form

Hello,

I going to give my users to give self sign up form how can i do it , pls help me to finish my project 

Thanks
Chinthaka

==== Required information ====
- iRedMail version:  iRedMail-0.8.3
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): LDAP
- Linux/BSD distribution name and version: Cent Os 6.3
- Related log if you're reporting an issue:
====