Wiser heads will provide better advice than I but, if your husband is a USC, he doesn't need to fill in a form (sorry if I'm telling you to suck eggs). But you will need to open your DS260 and update it with your husband's details.
To open the DS260, you will need to email the KCC (
KCCDV@state.gov ) and request for them to open your DS260. In order for them to do that, you will need to provide your case number, date of birth and full name. It will take a few days for them to respond. Update with your husband's details and then resubmit.
Oh, and congratulations on the wedding!