By the way, I found some good guide for 2-3 boxing on one PC
Beginners Guide 2 Dual-Boxing (3,4,5 boxing)

also that question of yours on General Forum should of been in IU & Macro Forum, there also few good guides on "How to?"

the most basic way to keybind a macro is to make one and put it on action bar, then open game menu, where says like "video" audio" "macros" and there also option for keybinding, I believe it called same thing "Key Binding", Find AsctonBar1 Button1(or what ever it called) and assign a key like 1 or Shift+1 to it (or what ever you want, as long as you don't break existing bindings, and know how to fix it back).

the other method to bind keys I already mentioned, Addons like bongos, trinitybars, bartender, BindPad, also will do the trick, but they also have learning curve, just have to play around with it, and you will be kaybinding in no time XD