Schema Registry Url for curl usage

Hi all, this feels like a silly question but I’m unclear if I am using the correct url to upload schemas to the confluent hosted schema registry. I plan to version control them and have CI upload them rather than the producer or UI.
The url and keys work on the producer config, but not with curl.

E.g. this command

    curl -X POST -H "Content-Type: application/vnd.schemaregistry.v1+json" `
        --user "${ApiKey}:${ApiSecret}" `
        --data "$SchemaJson" `  | jq

Fails with:
Failed to connect to port 8081 after 65188 ms: Couldn't connect to server

I am looking at the api reference here Schema Registry API Usage Examples | Confluent Documentation, but the examples mention localhost, so I am unclear.

Thanks in advance.

I feel you may want to refer to the specific documentation sections on Confluent Cloud, not Confluent Platform, where yes, everything is referring to an on-premise solution