Hello @Jino, CSS Selector is pretty easy to use. Though the preference is given to ID.
Anyways, here is a detailed way of using CSS Selector.
See the screenshot:-
Follow the steps from 1 to 7. This will get you the css selector for the element.
Then all you need to do is :
driver.findElement(By.cssSelector("#tsf > div:nth-child(2) > div > div.RNNXgb > div > div.a4bIc > input")).sendKeys("edureka");
Hope this helps.