Amazon S3

Create a dedicated IAM user for Allmount and give it access to one bucket only. Do not use your root account keys.

Access key and secret
Bucket name
Region like us-east-1

Steps

Sign in to the AWS console and open S3. Create a bucket, or pick an existing one. Note its Region from the bucket list, for example us-east-1 or eu-west-1.
Open IAM, choose Users, then Create user. It does not need console access.
On the permissions step, choose to attach an inline policy and paste the JSON below, replacing your-bucket with your bucket name.
Open the new user, go to the Security credentials tab and choose Create access key. Pick the use case for an application running outside AWS, or "Other".
Copy the Access key and Secret access key. AWS shows the secret once and offers a CSV download.

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": ["s3:ListBucket", "s3:GetBucketLocation"],
      "Resource": "arn:aws:s3:::your-bucket"
    },
    {
      "Effect": "Allow",
      "Action": ["s3:GetObject", "s3:PutObject", "s3:DeleteObject"],
      "Resource": "arn:aws:s3:::your-bucket/*"
    }
  ]
}

Next: open Allmount and pick Amazon S3. If something does not work, see troubleshooting.