Select Add permissions, to make sure your user has the required permissions to support the level of access required.
AmazonS3FullAccess - Grants access to all actions and all resources
AmazonS3ReadOnlyAccess - Grants read Get and List actions to all resources. This won't be able to write files from Zepl to S3.
Select Security credentials > Create access key
Download .csv file - This file contains the key that will be entered into Zepl's S3 Data Source. DO NOT LOSE THIS file.
AWS is constantly evolving - please review their documentation at (some link) to ensure best practice