Help with steps to installing a mod

This question has more than likely been asked a hundred times, but I still need to ask for help with installing Mods.  You download the mod as a rar file, but i am currently without a program to transfer it to something useful.  does it need to be turned into a .exe file? and after that is accomplished is it as simple as cutting and pasting it in the proper folder in the ironclad mod folder?  Thank you for your patience in explaining this process that is mind bendingly simple for yourself but bothersome for me.