Instructions to install Iron Chests Mod:
Make sure you have Minecraft Forge installed.
Locate minecraft application directory.
On the window that opens Run from the start menu, type% appdata% and click Run.
On mac open finder, press and hold ALT and click Library in the top menu bar. Open the folder Application Support and look for Minecraft.
Place the mod you just downloaded (.jar file) into the Mods folder.
When you launch Minecraft and click the mod button, you should now see the mod installed.