You will have to print and mail your tax return claiming the dependents. If you are owed a tax refund the IRS will pay the refund.
Within a year the IRS will investigate who was eligible to claim the dependents. The losing party will have to pay back any tax refund and pay penalties and interest.
See this TurboTax support FAQ for printing a tax return for mailing - https://ttlc.intuit.com/community/printing/help/how-do-i-print-and-mail-my-return-in-turbotax-online...
