When you say 'it is not working', what have you tried to resolve the problem?
Places to start. Open a konsole, run the command '/sbin/ifconfig' and post the results. This will show the status of all interfaces. You likely have a eth0, since you have a realtek ethernet card. It should have an IP address in the inet field on line two.
Can you ping your access point? From a konsole ping ipaddressofyourgateway. You should get a response.
If the above works, try a ping to
www.yahoo.com. I suspect that will not work, if it did you would not have posted this.
Try a ping to
If this works, you have a DNS issue.
Post as much as you can.