After following the instructions that pk gave you, you will still have self-employment tax on your U.S. tax return. See the following to remove the self-employment tax.
How do I pay zero Social Security (SS) taxes due to a totalization agreement?
You will not be able to e-file your tax return. You will have to print your tax return, sign it, and file it by mail. Attach the certificate of coverage from the Korean National Pension Service after all the IRS forms and schedules.
The instructions at the link above will remove Schedule SE from your tax return and remove the self-employment tax from Schedule 2 line 4. But one more step is needed, which TurboTax will not do. You have to write "Exempt, see attached statement" on Schedule 2 line 4. The only way to do this is to write the notation on Schedule 2 by hand after you print your tax return.
Since you have removed the self-employment tax, you might not have any other entries on Schedule 2, in which case it will not be included in your tax return. If that happens, print a blank copy of Schedule 2 and write the notation on it. Include it in your tax return after Schedule 1, or after Form 1040 if you do not have Schedule 1. If you are using the desktop TurboTax software you can print Schedule 2 from TurboTax in forms mode. If you are using TurboTax Online you can download a blank Schedule 2 from the IRS web site.
