使用Java和TestNG在WebDriver上同时在不同的操作系统和浏览器上执行测试

I have configured grid in my system and written my test script. I can run my test on any specified OS and any Browser but only on one OS and one Browser at one time not all OS and all Browser simultaneously. Here is what I have done. Please tell me how can I configure it so that it can run in configured OS in one time.I have configured grid in my system and written