You can begin introducing puppies to bowls of water once the puppy begins weaning off the mothers breast milk.
Puppies generally begin weaning off the mother dogs breast milk by age 4 weeks and sometimes as early as 3 weeks.
Once the mother starts weaning the puppies from her breast which is between 3 to 4 weeks of age then the puppies can begin drinking water.
So once your puppies reach 3 weeks of age be sure to keep some water in a bowl out for them that's easy for the puppies to drink from.
The puppies will then start learning to drink the water from the bowl by learning from their mother since they'll see their mother drink from a bowl of water.