Kittens should be nursed until they are four weeks old. (Ideally, they should be breastfed until they are one month old. In some countries, such as the US, it is recommended that kittens be breastfed for the first two to three months.)
From the fourth week onwards, mix kitten milk with a small amount of canned kitten food in a shallow dish and heat it to lukewarm (if using a microwave, only heat for a few seconds, stirring well afterward as microwave heating is uneven). Let them try and get used to the taste of the canned kitten food. Gradually, they will start eating from the bowl. Gradually reduce the amount of kitten milk and increase the amount of canned kitten food.
After a week, you can add softened dry kitten food (soaked in warm water) to the bowl and gradually stop adding kitten milk to the bowl, and reduce the amount of kitten milk in the bottle until it is all gone.
By six weeks old, kittens should be eating kitten food independently and drinking water from their bowl.
The entire process should be gradual and not rushed. (Do not use a cat food bowl that is too big for the kitten. Experience has shown that kittens often use oversized cat food bowls as litter boxes, defecating or urinating in them, or even standing directly in the food bowl to eat.)