As stated, it will be a "recovery rebate" and will be added to your tax return to increase your refund or decrease your tax owed.
Make sure you say the child lived with you the entire year (this is the correct answer for a newborn).
The child(ren) must have social security numbers for any tax benefits. Don't file until you get the SSN, even if you have to wait. If it will take longer than April 15 to get the SSN, be sure to file for an extension. Don't plan to file without the child and then file an amended return when you get the SSN. You need to file an original, on-time tax return that has the child's SSN.
