Json write a file

Maybe is a very basic question. But i cant figure it out how can i write a Json File using ofxJson.

the basic example only read:

void ofApp::draw()
{
    ofBackground(0);

    ofSetHexColor(0x00FF00);

    std::stringstream ss;

//    {
//        "firstName": "John",
//        "lastName": "Smith",

    ss << "firstName          = " << result["firstName"].asString() << std::endl;
    ss << "lastName           = " << result["lastName"].asString() << std::endl;

//        "age": 25,

    ss << "age                = " << result["age"].asDouble() << endl;

//        "address": {
//            "streetAddress": "21 2nd Street",
//            "city": "New York",
//            "state": "NY",
//            "postalCode": "10021"
//        },

    ss << "streetAddress      = " << result["address"]["streetAddress"].asString() << std::endl;
    ss << "city               = " << result["address"]["city"].asString() << std::endl;
    ss << "state              = " << result["address"]["state"].asString() << std::endl;
    ss << "postalCode         = " << result["address"]["postalCode"].asString() << std::endl;

//        "phoneNumber": [
//                        {
//                        "type": "home",
//                        "number": "212 555-1234"
//                        },
//                        {
//                        "type": "fax",
//                        "number": "646 555-4567"
//                        }
//                        ]
//    }

    int i = 0;

    ss << "phoneNumber:type   = " << result["phoneNumber"][i]["type"].asString() << std::endl;
    ss << "phoneNumber:number = " << result["phoneNumber"][i]["number"].asString() << std::endl;
    ss << "phoneNumber:type   = " << result["phoneNumber"][i+1]["type"].asString() << std::endl;
    ss << "phoneNumber:number = " << result["phoneNumber"][i+1]["number"].asString() << std::endl;

    ofDrawBitmapString(ss.str(), 10, 14);

}

how can i write the same file? arrays include.
Thanks a lot!