In the library, make your listing selections and click the Bulk Actions button.
The Bulk Actions button will appear towards the top right of your screen once at least one listing is selected.
Choose Library Actions, and then Export.
Next, you will be provided the options to save the export to your computer or open the csv file.
The export is limited to 250 products per file and this file may be used to edit your existing listings or as a template to create new listings.