Easy Step to Upgrade LinkSys WRT54GL with DDWRT

LinkSys WRT54GL is one of the wireless router that is popularly use as Wireless Access Point. In this article I want to share my experience when upgraded the router firmware with DDWRT. Before I upgrade the router firmware, may be there are some terms that must be known:
What is Firmware
In electronic systems and computing, firmware is a term often used to denote the fixed, usually rather small,