Dogs can safely take Pepto Bismol just like humans can however do not give a cat Pepto Bismol because it could harm them.
But if your dog is vomiting and you have some Pepto Bismol then yes you can safely give the dog some Pepto Bismol to help settle there stomach.
You can give your dog 1 to 2 tablespoons of Pepto Bismol per day which is a good enough safe dosage for the dog and if the dog continues to vomit after a few days you should take the dog to the vet.
Because something else may be going wrong other than just an upset stomach but if it's just an upset stomach the dog has causing the vomiting then the Pepto Bismol should help stop the vomiting within a few days and sometimes sooner.
I've given my dog Pepto Bismol before and he stopped vomiting within a few hours and fully stopped vomiting and felt better after a day.