You don't have to send the initial 1040 prior to filing the amendment.
You have to sign and mail the 1040X amended taxes along with any new tax document you received(like W2 or 1099)
See the link below on where to mail your amendment:
https://www.irs.gov/filing/where-to-file-addresses-for-taxpayers-and-tax-professionals-filing-form-1...
