To claim the carryforward credit from a prior adoption, you'll need to enter the child's information in the adoption credit section. You'll be asked questions about when the adoption began, when it was finalized, and whether you filed the Form 8839 in prior years for the same adoption. You'll also be asked for your current year expenses. Answer all of these questions appropriately and enter $0 for 2024 expenses. After entering all of the information for the child, you'll be asked about your credit carryforward. Enter the carryforward, or review the numbers to make sure it's reported properly.
If you don't enter information about the child, the Form 8839 will not populate and the credit will not be carried to the 2024 return.