Please read if you go to applossa plains (Whatever in the game during the day there is a little spot with the waterfall and wild horses stay there for the day Unicorns appear 12:00 to 5:00 (AM) if you stay there there will be a black unicorn, watch it for a while feed it then get to know it then you will have the desicion to adot it once you do, you have the chance to change it by clicking on it,
If you want a cheat, press shift ctrl and c at the same time type Testingcheatsenabled true
find a unicorn or wild horse hold down shift while clicking on it, press add to active family, Ta Da free horse or unicorn