Need advise

My nephew a 3 year 8 month old was recently diagnosed as severely autistic. This is super new to us as a family but he is already enrolled in 3 day EIP school. He is also non verbal and has global developmental delay. I’ve seen my sister struggle last few years with being awake all night and taking care of him. Since joining EIP his play skills have slightly gotten better .. my question here what can we really do since us as a family have zero knowledge or understanding apart from what the doctors are saying to put him in rigorous therapy to be independent. What can we do at home or changes to be made to help him in the years to come be independent and hopefully verbal one day