Visit the Netgear website (see
here for your router) and download the latest firmware file for the version of router you have. If you are not from the States click the
worldwide link at the top of their site to visit the page applicable to your country as the firmware is often country-specific.
The upgrade procedure is fundametally the same for most SOHO routers, however I recommend consulting the manual for the exact process. If you can't find the manual you can download a new one for free form the above link.
Once you have the file, log in to the router web interface (by default at 192.168.0.1) and write down all the settings you have configured as the upgrade will probably erase them. Some routers let you download a configuration backup file to your PC but unfortunately not all types will restore it properly on a new firmware version.
I'm not sure where it is on a Netgear but there should be a page for uploading the firmware file you downloaded, after which you click a button to upgrade the firmware. The guts of it happens automatically and can take a few mintues to complete.
Once it has finished, log back into the router and reconfigure all of your settings as required, or upload the backup file that you created earlier. Test that everything works and you should be done.
