install plugin for Open Distro

Amazon Elasticsearch Service offers k-Nearest Neighbor (k-NN) search which can enhance search by similarity use cases.

https://aws.amazon.com/about-aws/whats-new/2020/03/build-k-nearest-neighbor-similarity-search-engine-with-amazon-elasticsearch-service/

I tried this official code that I found here...

https://github.com/opendistro-for-elasticsearch/k-NN

PUT /myindex
{
    "settings" : {
        "index": {
            "knn": true
        }
    },
    "mappings": {
        "properties": {
            "my_vector1": {
                "type": "knn_vector",
                "dimension": 2
            }, 
            "my_vector2": {
                "type": "knn_vector",
                "dimension": 4
            }, 
            "my_vector3": {
                "type": "knn_vector",
                "dimension": 8
            } 
        }
    }
}

Getting this error:

"unknown setting [index.knn] please check that any required plugins are installed, or check the breaking changes documentation for removed settings"

How do I check if my Elastic installation supports this feature?