Form 8332, Release/Revocation of Release of Claim to Exemption for Child by Custodial Paren. What do I doo with signed form?

You cannot e-file form 8332, but you can e-file your tax return without form 8332.

Then, you (the non-custodial parent) must sign the form and mail it to the IRS along with the transmittal Form 8453 within 3 business days.