Postman is a chrome app. So it runs on chrome browser. So, before running postman you must install Google chrome. Here is the Google chrome link. http://www.google.com/chrome/
Now let’s install postman step by step. It is very easy.
Step 1: Type following URL and press enter
https://chrome.google.com/webstore/detail/postman/fhbjgbiflinjbdggehcddcbncdddomop?hl=en
Step 2: Click ADD TO CHROME
Step 3: Click App
Step 4: Wait a bit
Step 5: Click LAUNCH APP
Step 6: Now click sign in
Step 7: Sign in using google account.
Step 8: Launching postman client
Step 9: Choose GET as action and enter the URL: https://api.github.com/users/mahedee You will get following output as JSON format.
Step 10: Now if you enter the URL : https://avatars.githubusercontent.com/u/6042355?v=3 You will see the following output.
What we actually do here we installed postman REST client and then consume github api.