File it by mail. Print it, sign and date it in ink, and mail it in.
Use a mailing service like certified mail to track so you will know it was received since you will have a long wait.
Do not expect quick results from amending. It can take four months or more for the IRS to process an amended return.
You can watch for information here:
https://www.irs.gov/filing/wheres-my-amended-return