How do I set up a debit card on my child's Apple Watch?

My daughter just got an apple watch and we need to set up cards on her watch so that she can use apple pay in stores. She has a debit card with a company called Till and we have it in my apple wallet too. When we enter the watch app and go to wallet there are a few options that don't make a lot of sense. I need to know how I can connect my wallet to the watch app so that I can insert her debit card.