MKDIRP does have a permission to create new folder, how to give the permission?

I installed mkdirp to create new folder when the folder is not existed.

(Using npm install -g mkdirp)

But it seems like the mkdirp doesn't have the permission to create new folder,

when I try, I got this error,

{ [Error: EACCES, mkdir '/upload'] errno: 3, code: 'EACCES', path: '/upload' }

This is my code, and I'm using MAC

'fileUpload' : function(req, res, next){
    var mkdirp = require('mkdirp');
    mkdirp('/upload/image', function (err) {
        if (err) console.error(err)
            console.log ('!');
    });

How can I give the permisson to mkdirp to create new folder?