How do I add my IP PIN on my taxes that I e-filed?

[Opus 17]

If you transmitted your return, it can't be recalled.  Probably the IRS will reject it for lacking the IP PIN.  At that point, you can add the PIN and re-transmit the return.  The IRS will probably not actually start processing returns until late January (it will sit in the Turbotax data warehouse until the IRS opens e-filing.)