While making access token request from Headers, I'm getting below error.

Error- { "error": "unsupported_grant_type", "error_description": "grant type not supported" }

Am I doing something wrong or missing something? Please help!

Attached screenshot-

P.S. Check https://github.com/forcedotcom/postman-salesforce-apis out. It's bit more work to set the environment variables up, create an account with Postman to fork the repository... But in the long run saves reading documentation and typing all calls by hand.