Yes, so if I decide that it should be a universal maxim (whatever I want), I'm acting morally according to Kant? And if you want to answer this, please explain

Yes, so if I decide that it should be a universal maxim (whatever I want), I'm acting morally according to Kant? And if you want to answer this, please explain each key Kantian concept used, and you may find that you end up ultimately no where.