hi, i need help. new cactus parent

first post! how are you guys? i just wanted some advice on this zygocactus. i love and adore cactuses, but haven’t the slightest clue as to how to take care of em. i think its dying because there’s a purple brownish thing goin on at the tips of it, and i dont want it to. i just got it last week on Thursday, the soil feels moderately moist except for on one side. slightly crumbly. thoughts/advice?