Facing issue when use Lusitanian/PHPOAuthLib

Question

I'm new with Composer. I have added the Lusitanian/PHPOAuthLib with Composer and then I created psr-4 autoload directory and I made a class in that named OAuth.

I gave namespace which I want but I'm unable to use the PHPOAuthLib with my class, anyone idea what is the basic steps? Below is my code which I have written for Composer and OAuth class.

Composer code:

{ 
    "require": {
        "php": ">=5.3.0"
    },
    "require-dev": {
    "lusitanian/oauth": "~0.3"
    },
    "autoload": {
        "psr-4": {
            "MyOAuth\\NS\\": "app/base"
        }
    }
}

OAuth class code:

namespace MyOAuth\NS;

class MyOAuthNS
{

    public $client_id;
    public $client_secret;
    public $code;
    public $access_token;
    public $redirect_uri;
}