Well, you probably have Koha freshly installed and you have a big list of books that you want to get into it.
Koha requires that you do a regular cataloguing of your books, which is too time-consuming for most people. If your collection is pretty 'mainstream', you should be able to borrow MARC records from other libraries via Z39.50 search.
Rather than search for one title at a time, try a batch search. This video tutorial (opens in a new window) tells you how.
Download MarcEdit at http://oregonstate.edu/~reeset/marcedit/html/downloads.html