Go to this IRS website for a Form W-7 - https://www.irs.gov/forms-pubs/about-form-w-7
Go to this IRS website for how you apply for a ITIN - https://www.irs.gov/individuals/how-do-i-apply-for-an-itin
For a child to eligible for the child tax credit, the child must have a Social Security Number.
