If there is an agreement between you and the other parent (with a signed Form 8332) that allows you to claim your child as a dependent, you should enter them in your return. In this case do the following:
- Enter their personal information in the Personal Info section.
- Mark that the lived with you for less than 6 months (0 months).
- Continue to the screen that asks if there is a "custody agreement".
- Answer yes, there is a custody agreement.
- Answer no, the other parent will not claim them as a dependent.
If there is no agreement (no Form 8332) you should not enter your child's information on your return.