Use custom installation of openLDAP

[Ondrej Flidr]

Hello,
I'm trying to set kolab 2.3.0 to use our company LDAP server. Which 
schemas do i have to import? kolab2.schema and rfc2739.schema or 
something else? When i'm trying to import these two schemas, ldap server 
says

ldap_add: Server is unwilling to perform (53)
        additional info: no global superior knowledge

this error, AFAIK means "i need other schema".

So, is here any tutorial how to connect kolab with existing LDAP server? 
Thanks for answer

Ondrej Flidr
Universal Production Partners a.s.