@timelessfahad
The kittens will actually go to the pot filled with sand or "kitty litter" (material which can absorb the moisture and odor) and use it. Just keep their pot and they will use it in need.
My elder cats can actually use the squat toilet (desi toilet) too but these kittens will take time to learn that, plus they are so small that they can slip into it.
Don't worry, cats can learn a lot of stuff but they need a lot of care. Once you're adjusted with them, it's all fun.