ABOUT INTERNET SHARING

guys once again i want to ask question and need your help…

yesterday my cousin ask me for a hand because he bought another pc.. it means he has now 2 pc in there house… before he add the new one he has already an internet.. then he ask me to connect the two pc so that it will share internet.. as far as i know it needs a router then after that we connect it.. but nothing happens no internet connection at all//

the question is there any configuration to do in the router or in the computer so that they can share itnernet?