Under 15 lb dog owner here.
How young is the dog? What you train is what you get and if it's too late...
I was too young to care at the time and my mom/step-dad did what they bothered to do... well I'm just lucky my dog is submissive/quiet when I let him know I'm angry, only spontaneously barks for genuine new stimuli(somebody is at the door!) and has a thing for snapping at feet that enter his personal space(obvious solution: don't step on dog.) Unfortunately he never learned formal potty training so the best solution here is to walk him frequently, let him out into the backyard in between a few times, and just clean shit up when it happens.
He also developed I think a total dependence/pack lead mentality with me once I was the only one walking, feeding and playing with him 95% of the time. Coordinate your efforts with your dad, fast.