[Koha] how to delete a record?

[Silvia Soto-Bussard]

Dear All;
I am part of this support group and have asked before how can I delete a 
whole entry, this is, a bibliographic record.
I went to the address supplied for a Koha manual, but the item "delete 
biblio record", had not been developed yet.
So I have to bother you.
We do not use yet a marc record, as we have our own classification 
system in a small library of about 7000 books.
I need to do some deselection, and need to delete some titles, and/ or 
some second copies.
How is this done?
I have asked Chris last year if after doing this I could use 
that"barcode" number again. He said it should be possible, but I have no 
idea how to do it.
Many thanks for your answer.

Silvia Soto-Bussard
Librarian
Theosophical Society
Wellington