Error: Cannot find module 'newman'

I am trying to run a nodejs script where i am importing newman and running a collection. But, on compilation , it throws an error----

module.js:549
throw err;
^

Error: Cannot find module ‘newman’
at Function.Module._resolveFilename (module.js:547:15)
at Function.Module._load (module.js:474:25)
at Module.require (module.js:596:17)
at require (internal/module.js:11:18)
at Object. (/Users/sshekhar/Desktop/demo/script.js:1:76)
at Module._compile (module.js:652:30)
at Object.Module._extensions…js (module.js:663:10)
at Module.load (module.js:565:32)
at tryModuleLoad (module.js:505:12)
at Function.Module._load (module.js:497:3)

Please help!