You only have to copy it to:
/etc/e-smith/templates-custom/etc/ejabberd/ejabberd.cfg/85Modules
make your changes here and expand it with
expand-template /etc/ejabberd/ejabberd.cfg
For the changes itself I think these are the settings you have to change:
$OUT .= <<HERE
{ldap_filter, ""}
{ldap_rfilter, "((objectClass=posixGroup)"},
{ldap_ufilter, "(uid=%u)(objectClass=userJabberAccount))"},
{ldap_groupattr, "cn"},
{ldap_groupdesc,"description"},
{ldap_memberattr,"uid"},
{ldap_useruid, "uid"},
{ldap_userdesc, "displayName"},
I found some more configuration at
ejabberd mod_shared_roster_ldap Setup
{ldap_groupattr, "cn"},
{ldap_groupdesc, "description"},
{ldap_memberattr, "member"},
{ldap_memberattr_format, "CN=%u,OU=Users,DC=matrix,DC=example,DC=com"},
{ldap_useruid, "cn"},
{ldap_userdesc, "displayName"},
{ldap_rfilter, "(&(objectClass=group)(info=JabberRosterGroup))"},
{ldap_gfilter, "(&(objectClass=group)(info=JabberRosterGroup)(cn=%g))"},
{ldap_ufilter, "(&(objectClass=user)(cn=%u))"},
{ldap_filter, ""},
phpldapadmin from stephdl could help to find the right settings.