[SalesForce] 596 Service Not found when getting auth token from Marketing Cloud API

I have created a MC application (Component Type: API Application) so I can insert Subscribers into a Journey using API event.

Here is the scope

So I am stuck at the first hurdle, which is trying to authenticate. On the app detail page it provides "Authentication Base URI" which I have used to send my authentication request with the clientID and clientSecret inside the payload, however the server responds with "596 Service Not Found".

I'm not sure what I'm doing wrong, I've noticed the app status is "In Development", I'm not sure if this has something to do with it but I cant see how to publish it.

My payload looks like this…

curl -X POST \
  https://mcgg0286b-adfdgrttrtrhhfgh.auth.marketingcloudapis.com \
  -H 'Content-Type: application/json' \
  -H 'cache-control: no-cache' \
  -d '{
    "clientId": "asfwerwer12323",
    "clientSecret": "asdfasf32432432"
}