Macros are a built in thing you can use on any platform that can play XIV. It's basically a way to write out a series of actions, or just an action you want to work slightly differently. Pull up the system menu, the same one you would use to log out, and you should see an option to take you to a macro editor. Go to one of the squares are just start putting text in. For example:
Code:
/micon Aero
/ac "Aero" <tt>
Then you can put that on your hotbar like a regular abilities. In this macro, the /micon command gives it the icon of aero and makes the cooldown display as well. <tt> means "target of my target", which for me, usually works out to be the tank's target. So I'm targeting the tank, and aero/stone/etc will cast on whatever the tank is attacking.
Some guides that may help you get started with macros: text guide video guide alternate video guide