You Question Needs a lot of explanation , so i will summarize my answer :
First you should use Inspircd v2.0.15 because its stable , high performance and the most important for your usage , flagged as ldap support Link.
First :
You should edit your /etc/hosts file :
YouserverIp hostname.example.com hostname
Second :
Install OpenLdap :
sudo apt-get install slapd ldap-utils
during installation just type your ldap administrator password .
OpenLdapServer
Third :
Install apache2 : apt-get install apache2
Fourth :
Install phpldapAdmin : phpLDAPadmin (also known as PLA) is a web-based LDAP client. It provides easy, anywhere-accessible, multi-language administration for your LDAP server.
sudo apt-get install phpldapadmin
( that's why i installed apache2 , its web tool)
You have now two steps :
edit
/etc/ldap/ldap.conf
add : edit
BASE dc=yourdomain,dc=com
URI ldap://Your Ip Address
then : edit /etc/phpldapadmin/config.php



Just edit your Ip and domain name .
Open your browser :
yourIp/phpldapadmin
Enter your administrator password that you type when install sldap .
Now you connect to ldap database . select domain ----> on the right add Generic Posix Group ----> then select group and Create a child Entry add Generic User Accounts for testing .

More help use phpldapadmin Here
Fifth :
Now its time to configure inspircd :
edit : /etc/inspircd/inspircd.conf
you need to load the ldapauth module and point to your ldap server,
<module name="m_ldapauth.so">
<ldapauth baserdn="cn=test,dc=domain,dc=com"
attribute="uid"
server="ldap://yourIp or domainname"
allowpattern="Guest*"
killreason="Access denied"
searchscope="subtree"
binddn=""
bindauth=""
verbose="yes"
userfield="yes" >
You should also add you irc server name and admin name and other option in
/etc/inspircd/inspircd.conf
This tutorial would help you : Tutorial
Last :
Restart slapd , inspircd and try to connect be users you made .
Note change as it fits your needs , this configuration both irc and ldap are the same servers .
Hope it helps you because i don't think there is an official documentation could be simple as mine .