I currently have a litter of puppies (4 1/2 weeks old... 2 girls, 2 boys)... I started them on soaked dry puppy food at 4 weeks old... they are all doing great with it... Next week I will increase the number of feedings and put out Eukanuba dry food for them.
By 6 weeks they are usually weaned from mom and are eating less wet soaked dry food (the dry food is also available to them all the time).
I've had litters that didn't go for the soaked dry food so I fed them the canned puppy food at about 5 weeks... and sometimes topped it with a teaspoon of turkey or chicken baby food.
But 4 weeks is usually the starting period for getting them to start lapping "something".
Best of luck.