How to backup GitLab to the cloud (S3)

I am trying to follow the gitlab documentation to upload a backup to the cloud, but I find it sparse, and it isn't exactly straight forward.

Creating the tar is straight forward enough.

My problems start with

For omnibus packages:

gitlab_rails['backup_upload_connection'] = {
  'provider' => 'AWS',
  'region' => 'eu-west-1',
  'aws_access_key_id' => 'AKIAKIAKI',
  'aws_secret_access_key' => 'secret123'
}
gitlab_rails['backup_upload_remote_directory'] = 'my.s3.bucket'

What am I supposed to do with this? I place it inside /var/opt/gitlab/gitlab-rails/etc/gitlab.yml just so, is that what I do?

  multipart_chunk_size:
  encryption:

  gitlab_rails['backup_upload_connection'] = {
    'provider' => 'AWS',
    'region' => 'eu-west-1',
    'aws_access_key_id' => 'AKIAKIAKI',
    'aws_secret_access_key' => 'secret123'
  }
  gitlab_rails['backup_upload_remote_directory'] = 'gitlabbackupxan1234'

  ## GitLab Shell settings
  gitlab_shell:
    path: /opt/gitlab/embedded/service/gitlab-shell/

Then we come to

If you are uploading your backups to S3 you will probably want to create a new IAM user with restricted access rights. To give the upload user access only for uploading backups create the following IAM profile, replacing my.s3.bucket with the name of your bucket:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "Stmt1412062044000",
      "Effect": "Allow",
    ...
      "Resource": [
        "arn:aws:s3:::my.s3.bucket"
      ]
    }
  ]
}

Again, how? I started reading about AIM but it is a big topic and I am not quite sure what to do with this.