how to create aws stream with cli input json file

Hi,

I am trying to follow the instructions in (https://docs.aws.amazon.com/iot/latest/developerguide/mqtt-based-file-delivery-managing.html) to create a stream for my application purpose. however, when following the instruction in the doc, I was stuck at trying to following step (https://docs.aws.amazon.com/cli/latest/reference/iot/create-stream.html), there's a json file as follows, how do I create this json file ? Thanks in advance.

Contents of create-stream.json:

{
    "streamId": "stream12345",
    "description": "This stream is used for Amazon FreeRTOS OTA Update 12345.",
    "files": [
        {
            "fileId": 123,
            "s3Location": {
                "bucket":"codesign-ota-bucket",
                "key":"48c67f3c-63bb-4f92-a98a-4ee0fbc2bef6"
            }
        }
    ]
    "roleArn": "arn:aws:iam:123456789012:role/service-role/my_ota_stream_role"
}