Please help! My kitten WONT litter train & is pooping all over the house HELP!!?

If her and the older cat get along pretty well together, put her in the litter box when the older cat gets in it. That is how I taught all of my kittens to use the litter box. Sometimes cats are really picky about their litter boxes. Maybe they don't like the litter or they don't like the hooded one, or they don't like the location of the litter box or maybe she wants her own litter box. My cat Precious ( my avatar is a picture of her) absolutely refused to use the litter box and then I took the top off of it and now she will use it.