Reply

Do you mean you did not provide your sister's family members information in Part 4 of the I-130 when you file it? 

If yes, then when National Visa Center (NVC) contact you to request you to provide the immigration visa documents and pay the fee in the future, you just need to create the online account in NVC website and then, add your sister's family members (spouse and kid) into NVC online following the instructions at this link (Read "How do I add a derivative family member to my case"):

CEAC FAQs (state.gov)