Configure your router accordingly. The idea behind a (home) router is that you have a device which lets your share the WAN connection between multiple other devices and router traffic accordingly. You connect your ISPs cable to the WAN port and every computer that should be part of the network to one of the available LAN ports.
Every computer gets some kind of internal address like 192.169.100.X
usually automatically assigned using DHCP. That DHCP configuration also supplies additional information e.g. that your router should be the default gateway for those computers. That was traffic that isn't meant for the internal network gets send to the router and the router forwards it to your ISP.
If you can not ping or otherwise reach the other computers that are part of your LAN (assuming they're all connected to the LAN ports of the router) you need to check the configuration for isolation options. This depends on the model of the router so without knowing which model of router it is you're on your own on that.
I don't really understand your problem. Configure your ISP access data on the router and let it handle the internet connection? – Seth – 2016-11-23T08:37:17.307
My ISP provides RJ45 connection when i connect it to my computer, I can connect with my friends play cs etc. as they are on the same network 192.169.100.X. However, for using router I need to insert RJ45 into WAN port. which gets WAN IP from ISP. Hence I do not have access to local computers ie network 192.168.100.X. My query is, is there any way configuration or something to bridge WAN and LAN ports so that i can access 192.168.100.x thanks in advance – Er Bison – 2016-11-23T08:53:18.873