API Authorization Not Working

Hello, I wanted to authorize the unity simulation swagger API given in https://github.com/Unity-Technologies/Unity-Simulation-Docs. I couldn't find any command for authorization, apart from the "authorize" tab at the top right of the page. It does authorize but the client id is hidden. I want to connect the API to my app, for which client id is needed. I tried to run the command for authorization as given here since the above API's look similar. https://docs.gamesimulation.unity3d.com/

It gives me this error on giving
> curl --header "Content-Type: application/json" --request POST --data '{"username":"blahblah","password":"hello","grant_type":"PASSWORD"}' https://api.unity.com/v1/core/api/login > { "message" : "Input Error", "code" : "143.002" }

My auth credentials are correct surely. Still this error. Would very much appreciate if you can help me find a way in getting the client id for auth or resolving this error.