If there is no ISBN number try to search on the LC card number. This may result in multiple hits and you will have to distinguish between them for the best, or matching record. In the fixed field look at the ELvl. ELvl is 4 leave it. 020 field - ISBN number for books.
Field is repeatable.
Type REF or JUV as first line of call number on the label for the item. If the book is for any other area of the collection do not catalog . Place on hold shelves until in system. Make sure it matches your book. When in doubt please ask.