Help adding infant to DEERS

My husband is going to be away on a training mission or TDY whatever it’s called and our daughter will be born while he’s away. We aren’t sure if he’s coming home for the birth but I wanted to know how would I add her to DEERS? Do I need a POA? If this helps, my husband will be working 8 hour days in Texas and will have access to his phone and internet and will be able to add her by calling or by going online if needed. Do you think we will have an issue adding her? I’m not sure how it’s done because he added us when he went to basic last year and our son was already born at that time. Will he have to be in an actual office to add her?