Before you can connect your Amazon Marketplace, you need to activate your FeedbackWhiz account and confirm your email address.
After your FeedbackWhiz account has been activated, log in to your FeedbackWhiz account and go to YOURNAME > Account Settings > Marketplace Settings
https://app.feedbackwhiz.com/account/settings#!/marketplace and click on the "Connect Amazon Seller Account" button (Choose your appropriate marketplace by clicking on the tabs next to North America)
You will see a popup (as shown below) that will guide you on how to connect your Amazon account.
For Step 1: Once you click on the "Authorize FeedbackWhiz" button, you will be redirected to the Amazon Seller Central page where you will authorize the FeedbackWhiz application.
Make sure the checkbox is checked and then click on the Confirm button.
You will be then redirected back to the FeedbackWhiz Marketplace Settings page again.
For Step 2: Enter your registered or approved Amazon Seller email address used to communicate with your buyers. If you are not sure please go to View Registered / Approved Emails
For Step 3: Select the amount of order history you want to initially sync.
Click Connect to finish.
Note: It could take a couple of hours to download all of your Amazon Seller Account data. A notification will be sent to inform you once all your orders are synced.