Selenium automation for new window pop up

Ashish,

I was trying web automation for site "https://www.online.citibank.co.in/". After page loaded successfully, I clicked on "Login Now" button and page navigates to a new web page when user has to enter Username and password field.

When I try to input value in user id I got error message as below

org.openqa.selenium.NoSuchElementException: Unable to locate element: {"method":"xpath","selector":"//*[@id='User_Id']"}

below code I was using to enter user id and password

driver.get("https://www.online.citibank.co.in/");
driver.findElement(By.xpath("//*[@id='container']/div[2]/div[2]/div/div[1]/div[1]/p[2]/a[1]/img")).click();
driver.findElement(By.xpath("//*[@id='User_Id']")).sendKeys("123456789");
driver.findElement(By.xpath("//*[@id='password']")).sendKeys("12345432");

Can you please guide me how can I rectify this issue

Thanks,
Sumanta