To dispose of kitty litter or cat litter you can just simply scoop the used cat or kitty litter into a plastic bag such as a plastic grocery bag or other trash bag and then tie the bag shut and place the kitty litter into your garbage.
Kitty litter is basically just clay and can be disposed of in your regular trash.
You can also put the kitty litter onto the ground in your yard and dispose of it that way.
I used to just dig a hole in the ground in my backyard and then pour the used kitty litter into the hole and once filled I would cover the hole back up with dirt.
But when I lived in an apartment I would just put the used kitty litter into a plastic bag and throw it in the trash.