You will need to download the latest version of the mod.
You will also need a program such as winrar to open the compressed mod file.
(winrar is a free to download application that is very useful for opening many files downloaded off the internet.)
"To install, browse into where you have Republic commando installed. Then browse to:
\Star Wars Republic Commando\GameData\Textures
In the textures folder make a backup of: hudtextures.utx
and replace it with hudtextures.utx from the 16-9 folder."
In future releases the installation instructions may change.