That documentation is telling you how to configure this, and even has instructions for Postman.
It is using the password grant type.
On a side note, password credentials for this type of “service account” connection is unusual. It would normally be client credentials.
Password is normally used when you want to authentice with multiple roles and permissions. If its a single service account controlling access, then client credentials is more appropriate.
However, you can either use the authentication helper like the documentation is guiding you through, or you can create this as a normal request like the following.
Then retreive the token in a post response script.
Something like.
response = pm.response.json();
pm.collectionVariables.set("bearerToken", response.id_token); // used in the authorisation header bearer token
You would then consume the token by setting it in the auth tab for the subsequent requests.
