For macros, you equip these like you do main abilities, the game figures out the right bar. For example, my fisherman (these are like Masterpiece for the crafters): /eaction 1 "Veteran Trade" and /eaction 2 "Nature's Bounty". This puts them in slot 1 and 2 in the abilities bar.
Masterpiece you actually use in crafting, watch for the scroll bar to head down below 'wait', and you'll see it there.
For the gathering ones, like already mentioned, they trigger randomly.
XIV: Misfit Stormrider - Kashuan
XI: Kujata - Razoredge (Long Retired) A possible retainer idea