First, log in to the cobby portal at app.cobby.io.
Your store has to be already created in the portal. If you haven’t created a store yet, you can find instructions here for Magento 1 or here for Magento 2.
Under Shop (1) you will find a download link for the Excel plugin (2).
You can open the downloaded file with a right click.
Now another window appears.
Click on Install → wait until the download is completed → Close
Open Excel, click on cobby (1) and Load products (2).
Now all store data will be loaded into the Excel file and you can start editing.