[Koha] Reading Levels

Good morning, I am trying to add the ability to search by reading levels into my catalog. Can anyone let me know how to make the 521 tag be searchable and then if I could edit the OPAC in a web program such as GoLive in order to let the patrons search this field? Thanks Darla -- Darla Grediagin District Librarian Bering Strait School District Unalakleet, Alaska Web Address : http://bssdonline.org/course/view.php?id=51 Blog: http://aklibrarian1.edublogs.org/