From the Amazon Advertising main dashboard scroll down, until you see the table where your campaigns are listed. Then select the campaign, where you want to export the keywords. The screen should look similar like this:

On the right side at the top of the screen select ‘Date Range: Lifetime’. This is important, otherwise, you don’t have all the data in your exported file. Now, scroll down until you see the screen below:
Click the ‘Export’ button next to the ‘Columns’ button and then follow the instructions on the screen to download the file to your desktop. We recommend that you change the file name to the campaign name, once your file is downloaded. Amazon gives your export file an arbitrary file name, which does not contain the name of your ad campaign.