We make a new project in Eclipse and then go properties ->Java Build path Add external jars and add all the the selenium jars from the lib folder and also the node file outside the lib folder.

Then for firefox driver in eclipse we go to this link https://github.com/mozilla/geckodriver/releases and in downloads section we download this file geckodriver-v0.10.0-win64.zip Then we extract this file and put the gecko driver somewhere in our project and then we have to put Firefox driver command in eclipse as in selenium 3.x this gecko driver is introduced . It was not there in previous versions of selenium.

Same way we can do for chrome and i.e we can download the driver from selenumhq.org