errors output from ldapadd command

[<anmais@in.gr>]

Dear friends,
Congratulations for your usefull work!
My name is Antonis Maisoglou and I'm a student of Technological Educational Institution in 
Thessaloniki(Greece).First of all sorry for my bad English.
I've taken up a project about directory services.I downloaded openldap-2.0.23 from
your site and I started to configure my database.However,when I run the command
ldapadd in order to add an entry,the output of this command is:
ldap_add: object class violation
          additional info: attribute 'mail' not allowed
ldif_record()=65

Additionally,
 ldap_add: object class violation
          additional info: unrecognized objectclass 'inetOrgPerson'
ldif_record()=65
Would you be kind enough to give some help about these errors?
Thanks a lot and sorry for your usefull time.