To help litter train your cats you want to have one more litter box than you have cats. So if you have two cats you want to have 3 litter boxes. You want to have the boxes in locations where it is easy for the cats to see what is going on around them. When they are using the litter box it is a very vulnerable time for them. Having them in the open helps them to feel more secure. Experiment with different types of boxes and litter to see what your cat likes. To get them oriented to using the box. Take them and rub their pads in the litter. This will leave their scent in the litter and help them feel more comfortable using the box. Make sure you clean the boxes everyday. They do not like dirty boxes. If they leave you presents they are trying to tell you something about the litter box set up in your house. So experiment until you find a comfortable set up for them.