1. let the father show him how to pee
2. buy 6 more underpants, do NOT wear pull-ups(片褲). Best time for training is summer as clothes dry faster. Wear only undepants at home. Use pull up when going out.
3. teach him to say "shu shu"
4. he will wet his underpants and the floor for a few days/weeks. Take him to the toilet every hour until he can say shu shu. Praise him if he does not leak, but do not scold or beat him if he leaks. Just say "shame shame".
My son stopped leaking after 2 days. Some kids take longer.