The same way you potty train a dog with sight. How long have you had the dog? Some dogs always "go" inside. Provide an area for the dog. Spend more time with the dog outside. Give the dog lots of praise. Dogs do like to smell around, and this is really important for a blind dog. Be patient. Let the dog smell around outside as long as it wants. Make sure you clean your carpets, because if the dog continues to smell the scent of its urine/poop on the carpet, he'll continue to go there.