How Do I Potty Train My Kitten?

My kitten is about 3-4 weeks old. She seems to have a good bladder control, but she has been having accidents in the house for months. I’ve tried changing her diet and giving her Science Diet Kitten Complete dry food (the only thing that I feed because it’s all she’ll eat). The vet said potty training shouldn’t be too hard with such a young cat, so we’re going to try again after she’s had another round of shots next month. My question is: how do i potty train my kitten? Do you give them rewards when they go outside? Rubbing their bellies after they go out might work as well!