The
amendment starts with your figure from your original return and begins fresh
with the changes you input.
You cannot amend your original return until IRS finalizes your
return and you receive your refund.
You will mail your
amended return to the IRS. They do not accept electronic amendments.
The following IRS
link is very helpful in understanding the amendment process.
https://www.irs.gov/newsroom/amending-your-tax-return-ten-tips