//Click on link which will open new Link
driver.findElement(By.linkText("Search settings page")).click();
// Now we have two windows and store them in to object array
Object[] currentWindow =driver.getWindowHandles().toArray();
//In the array, first index is Parent window next is child window
String ParentWindow=currentWindow[0].toString();
String ChildWindow=currentWindow[1].toString();
//To work on child window
driver.switchTo().window(ChildWindow);
//Now you are in child window, If you want go back to parent window
driver. close() // It will close the child window. (Optional.If you dont want to close the first window, this step is not required.)
driver.switchTo().window(ParentWindow);