Install phpldapadmin, this is a good gui to see your ldap tree.
Next you will need to add the samba.schema file to your ldap system. Do a google search for this but NOTE - the newer version of LDAP does not use the ldap.conf file to import schema files, it instead uses cn=config. I think this is as of 2.4.11 so make sure the tutorial you use is correct for your version.
Next you need to install samba smbldap-tools smbclient samba-doc. once installed you need to populate your ldap tree with the samba files using one of the tools provided by samba-tools
Have a look here (note that adding the samba schema file may not work for your LDAP version)
Once that is done you can add a user like this
smbldap-useradd -a -m john