Postman is chrome browser extension, so you can download and use in chrome.
Let's try the api call with token authentication if you are ready.
1. Enter token endpoint with "POST" and "x-www-form-urlencoded" options. Also enter "grant_type","username" and "password" to request token.
2. Click "Send" then we could see the result. Copy the actual "access_token" data string highlighted.
3. Now we can request get/post with bearer token header. After entering the api url, select the "Headers" button and fill the "Authoriaztion" with bearer <copied token string> input as following image.
Click "Send" button and we can see the JSON result!