The first one is your AWS account number - if you log in to the AWS console, it will either show up in the top right, or you can click the down-arrow and copy the Account ID. Ignore the dashes though. The second is the name of the IAM user you've set up.
You don't set these in the RDM - you set them in a policy within IAM in your AWS account.
If you're struggling to set this up, I'd make a suggestion that you set up an SFTP server and have RDM push files to you that way. It's much more visible than pushing to a bucket, and so much easier to troubleshoot.
Peter