Hey /adv/ I have absolutely no idea what I'm doing with plants as I have never owned one before. I recently received a moon cactus that's in a pot from home depot. How the fuck do I care for this thing? When do I water it? I am keeping it in this pot.
Those grafted cacti are a pretty bad choice for a first cactus and are pretty much guaranteed to suffer slowly or die quickly. The only advice I could give would be to change the soil to a better draining and peat less kind and water infrequently during the growing season and not at all during the dormancy period which is winter for most cacti. Also they like a fair bit of light but not direct sunlight.
If you're actually interested in cacti you'd be better off owning non mutant cacti which are far more rewarding and will last your entire lifetime.