Our Bichon is 2yrs 8mths old. We got her as a puppy. We trained her to go outside or on a pad. She mostly goes outside. Once in a while she will go on a pad...smack in the middle. We keep a pad out if we are outside & she is in by herself. She 99.9 percent of the time waits until we take her out. We had her trained when she was a puppy. When we think she has to go potty, we say potty outside. We take her out & say potty. After she goes..we say good girl potty outside. When take her in & give her a treat. If it is bad weather out, we say potty on pad. After she goes we tell her good girl potty on pad & give her a treat. As we give her a treat, we say good girl potty outside or potty on pad. Give praise...that works the best. When your dog goes in your house. Tell your dog bad girl or boy & put the dog in a pen just for maybe 5mins or so & then let the dog out. They say if you put the dog in a pen too long they will forget why they were put in there.
We taught our Bichon Zoey to go in a litter box. We didn't have her from a puppy, we got her from another home when she was about 6 months, and she was always having accidents in the house. Along with this she hated going outside to use the bathroom, especially if the ground was wet or it was raining, the little spoiled princess haha. Someone suggested trying the litter box to us and she took took to it within days. I really suggest having either a puppy pad or try the litter box, it worked for not only us but for her litter mate as well.