[Koha] newbie needs help importing records

[Shelley & Kurt Kemperman]

We have just downloaded and installed koha for use in our small  
Catholic school library.  We have no current computer records for our  
books (about 4000 items).  I am not a techie or a librarian, but am  
trying to get this set up.  I could really use some help in how to  
start importing MARC records via a z39.50 server.  I am lost in all of  
the manual directions about MARC identifier fields, etc.  In my  
perfect world, I would like to take a book off of the shelf, search by  
title in the Library of Congress or other database, import the MARC  
record, stick a bar code sticker in the book and scan it.  Can anyone  
help me access some basic  directions for this or get me started?

Thanks so much
Shelley