Flashback Trojan

F-Secure says that you should type this (the lines below) in something called the "terminal"

"For those who want to check if mac is infected (from F-Secure instructions):
Run the following command in terminal:

defaults read /Applications/Safari.app/Contents/Info LSEnvironment
defaults read ~/.MacOSX/environment DYLD_INSERT_LIBRARIES

If you get "The domain/default pair ... does not exist" for both - you are clean"

I really don't understand how to use computers besides things like iTunes and Safari.

My question is that what if typing that stuff into the terminal thing screws up your Mac or gives you the Flashback thing. How do you know that F-Secure is legit?

I want to check to see if I have the Flashback trojan but I'm not sure if I should type that stuff in.