do you already own a shipcloud.io account? If not please register here: https://app.shipcloud.io/en/users/sign_up?plan=basic. After doing so, you will get an API Key which is required for the addon to work properly.
Once you have done that, insert the API Key in the addon configuration page (http://your-suitecrm-instance/index.php?module=JAK_Jakota_Shipcloud_Connector&action=config) as shown here:
After you've done that you can start relating modules.
Afterwards you can create stamps via EditView or in the subpanel of the related module.