The main dought (confusion) is what exactly I need to pass in the body of the POSTMAN as in this documentation https://api.qualtrics.com/api-reference/docs/Instructions/Quick%20Start/qualtrics-api-quick-start.md it is just said to paste the "grant_type:client_credentials" but the error which I am receiving is 400 BAD REQUEST(Request was malformed. Error details are in the body content. Most often the request body contained an invalid parameter or definition.) I'm totally confused what I'm missing or what mistake I'm making can you please help me out.....
This is the error received in POSTMAN
{
  "error": "invalid_request",
  "error_description": "The request is missing a required parameter, includes an invalid parameter value, includes a parameter more than once, or is otherwise malformed",
  "error_hint": "Make sure that the various parameters are correct, be aware of case sensitivity and trim your parameters. Make sure that the client you are using has exactly whitelisted the redirect_uri you specified.",
  "status_code": 400
}

prathyusha I am having the same issue. Did you find a solution?

prathyusha : You need to connect to the correct data center. This fixed the problem for me.
https://api.qualtrics.com/instructions/docs/Instructions/base-url-and-datacenter-ids.md

When I was doing this in POSTMAN, I had to create a 'header' with the X-API-TOKEN key using the API Token value found in Account Settings and Qualtrics IDs; if you don't currently have an API Token listed, you can generate one with the provided button.