Until your return moves into accepted status, you won't be able to amend. In fact, you won't be able to do anything with your return. If you're amending to claim more money, the IRS says to wait until you've received your original refund before filing an amendment.
Once you've received your original refund, feel free to cash or spend it while your amendment gets processed (this can take 12–16 weeks).
Three weeks after you mailed your amendment, you can start tracking its progress at the IRS Where's My Amended Return? site.
The IRS Form 1040X for 2017 won't be available until late January or early February 2018. To check back and see if Form 1040X is available, click on How to amend (change or correct) a return you already filed.
[Edited 1-22-18|7:24 am PST]
