如何使用selenium webdriver自动化弹出对话框窗口

I want to automate some report. When clicked on some element it will open popup dialog window but I won't get an access elements from it. Because, code will be running at parent window it can't go to the newly opened popup dialog window and when I closed the browser I got an error, but I won't get any message in the console.I want to automate some report. When clicked on