I'm probably being too basic here: there are two parts to a catalog record (at a really basic level), and these are edited in two different places
1) The MARC21 record - the fields for this are edited from 'Edit > Record' and there are lots of MARC tags and subfields to enter information for, such as the title, author(s), and so on 
2) Individual item information for that record, listed under the 'Holdings' table (as you may have multiple copies of the book, for example), such as location, barcode, copy number, and so on for that individual item - this information is edited from 'Edit > Edit items' (or alternatively, edit directly from the 'Holdings' table using the Edit button next to each item)
If you are not seeing these areas/menu options, then something is not quite right - it's hard to describe this using just text!