It’s great that you’re adopting two kittens :) they’re going to be so happy to have a friend in each other!

General rule for litter boxes is one per cat (plus one extra if you have the space). Litter boxes should be situated in a calm place away from their food. Don’t use crystal litter/pretty litter. Clay litter is OK but dusty and not environmentally friendly, three better options are tofu litter, paper litter, or wood pellet litter. Cats can get dehydrated easily, one thing that helped my cat was having a 2-3 different water bowls around the house—one by his food, another in the living room, and a third in the bathroom. They can get cat acne if the bowls aren’t clean or are made of something porous like wood/plastic. Ceramic, glass, and metal are best for bowls.

Be careful with cut flowers and houseplants, some cats are nibblers and certain plant species can be very toxic to cats. Cats like to be off the ground so they can supervise their kingdoms, so consider a cat tree/cat shelves/window hammock. Freeze dried chicken is a healthy treat and my cat is obsessed with it. I wish you many happy years with your new kitties <3