@MIYF
It's not clear from your post whether your tax is changing due to your error.
If your tax has not changed,
get Form 1040-X from IRS website and mail it in with your 8606, which you can also get in fillable PDF.
Note: since you are not changing any dollar amounts on your amended tax return, you can leave all the lines 1-23 EMPTY.
Part III explanation: "didn't include Form 8606 with e-File".
