Get there: More > Tools > Catalog > Stage MARC records for import
Importing records into Koha includes two steps. The first is to stage records for import.
First find the MARC file on your computer

Next you will be presented with options for record matching and item imports

Enter 'Comments about this file' to identify your upload when going to the 'Manage Staged MARC Records' tool
Choose the character encoding
If you leave this set to Default Koha will try to guess the encoding, but it should be noted that this is almost always wrong for non-UTF8 records with non-ASCII characters. Specifying a character set is much more reliable if you're not using UTF-8.
Choose whether or not you want to look for matching records
You can set up record matching rules through the administration area
Next choose what to do with matching records if they are found
Finally choose what to do with records that are unique
Next you can choose whether or not to import the item data found in the MARC records
Click 'Stage for import'
You will be presented with a confirmation of your MARC import

To complete the process continue to the Managed Staged MARC Records Tool