what phone do you have?if you wish to mod it then just go through one of the tuts either here or at SE-NSE Home, because before you can enter FAR you need to flash your firmware with a ssw file and then do your things in FAR then flash it with a rest(restore) file.
I'd recommend you go through the entire procedure by reading one of the tutorials! That way you can be sure about what you are doing and hence have lesser chances of bricking your phone! :D