Like FTP, TFTP requires you to use a client program to talk to the receiving device. Operating systems like Windows have a command line utility called 'tftp' that functions as the client. Linksys provides a free TFTP client with a graphic interface (GUI) that you may prefer using instead of the command line.
The Linksys TFTP client (see right) offers similar functionality to the command line. Through their utility you specify the location of the firmware .bin file, the router's administrative password, and its IP address. The client displays status and error messages as would appear on the command line, and the GUI can be set to automatically retry a firmware download if it fails on the initial attempt. The client also works with other TFTP capable routers, not just Linksys ones.
Unfortunately, even though I could ping the router I was troubleshooting at its default address (192.168.1.1), the router's TFTP server was not functional and I was unable to establish a TFTP connection through either the Linksys GUI or Windows command line. It happens.→ More - Linksys TFTP.exe Download (ftp.linksys.com)
→ See also - Upgrading Firmware on a Wireless Router
Linksys TFTP Client for Firmware Upgrades - Version 1.255 - Graphic: Bradley Mitchell / About.com