Add your basedn to basedn (eg: echo o=denkn,c=at > basedn).

For initialization, first shutdown slapd and delete /var/lib/ldap/ (you will loose all of your data!), then use ./90.root.ldif | slapadd -b \cat basedn` -v`.

Now you can start slapd again.

Via ldapadd -Y external you can add any other ldif.

For adding an user run ./90.user.ldif.sh username givenname surname emailaddr | ldapadd -Y external.