I dont have a green thumb. Correction.. I have to research and carefully care for plants but can make some grow in a garden.

Need your help with this one.

I was given this cactus thing that is supposed to bloom once every 100 years. The people that gave it to me were thinning theirs out and offered it and I accepted but said it may end up dying. Id like to do what I can to give it a chance to grow and thrive and potentially bloom decades from now, but I dont even know if ive potted it right, or what kind of soil or how much water. More dirt? Less?

So if you have advice, please let me know. I just bought this pot today and used some dirt I had been using in garden.