how to play code red: battle for earth

[Sridhar_Rao]

Hello guys, I have never played a computer game since I have owned a computer. Recently, I tried to play the freeware Code Red: battle for earth provided in digit CD. I killed few of the aliens, got inside the ship and reached a chamber where all the aliens seem to be inside a glass chamber or so. I am stuck at that, I don't understand how to proceed with the game. Any idea please, also it would be kind if anyone could explain me the game, the controls (keyboard) and what to expect in the game.

Please don't aske me to refer the help. Forgive me for being so dumb!