Go to Koha administration > Basic parameters > Authorized values.

This will take you to a new page with a table of authorised values on your site. Use the search box at the top of the table to search for ccode. This will narrow the table down to only the Collection Code option. Click the CCODE option under the Category column.
This will bring you into a table of existing Collection Codes on your site.
This page gives you an opportunity to review existing Collection Codes on your site before adding a new one.
To add a new Collection Code, click the +New Authorized value for CCODE at the top of the page.
This will open a form of information that can be filled out to add a new collection code to the site.
Authorised value
This is a unique code to represent the collection and the format should be similar to the codes already defined in the table. For example, if the collection code already defined take the format of FIC, for Fiction, then the other values should generally be three figures for the start of the word.
Description
This is the name of the value as it will appear for staff members.
Description (OPAC)
This is the name of the value as it will appear on the OPAC.
Library limitation