How to use macro is a VERY broad question. However, I bet if you search for a video how to download macro, you'll find one :)

 

http://www.ecocitycraft.com/forum/threads/how-to-install-macro-mod-optifine-for-1-6-2.63815/

Spoiler: macros

http://www.ecocitycraft.com/forum/threads/simple-coordinate-display-macro.47595/

http://www.ecocitycraft.com/forum/threads/mcmmo-display-macro-tutorial-finished-august-6th.57543/

http://www.ecocitycraft.com/forum/threads/autosprint-for-macromod.49786/

http://www.ecocitycraft.com/forum/threads/macro-mod-script-unbreakable-tools.65587/

http://www.ecocitycraft.com/forum/threads/very-simple-chat-clearing-macro.66144/

http://www.ecocitycraft.com/forum/threads/macromod-updated-balance-display-macro.53376/

http://www.ecocitycraft.com/forum/threads/macromod-chat-channel-display.54815/

http://www.ecocitycraft.com/forum/threads/macro-mod-basic-armour-durability-display.55920/

http://www.ecocitycraft.com/forum/threads/simplest-item-durability-display-macromod.47047/

http://www.ecocitycraft.com/forum/threads/easy-repair-loop-for-macro.47031/

http://www.ecocitycraft.com/forum/threads/macromod-lottery-pot-display.55913/

http://www.ecocitycraft.com/forum/threads/afk-display-macro-tutorial.67591/