If you are the non-custodial parent, you will mail the signed original that you received from the other parent to the IRS after you e-file, along with a cover letter that Turbotax will tell you to print. Or, you can print and mail your entire return along with the signed original form. (Keep a copy for your records.)
If you are the custodial parent and you need to issue this form to a spouse, you must give them a signed original; either in person or by mail or something else. You can probably print it from inside Turbotax under "other tax situations" or download a blank PDF from the IRS web site.
