If you already submitted your return, then you will have to wait until your return has been accepted by the IRS and the amended forms are available then you can Amend Your Return
The IRS is not accepting e-file returns yet. If you file or submit your return now, it goes into a "holding tank" until the IRS opens their system to accept the e-filed returns. As of right now, any returns submitted are basically sitting in the post office waiting to be delivered. They are expected to start accepting them the end of January or up to mid February. The exact date has not been announced yet.
Amended forms are generally not available finalized and available until mid- March so, you will need to wait until then if your return is accepted to amend.
However, if your filing is rejected for some reason, then you can fix it and resubmit.
(Edited to add]: It's also possible that the IRS will adjust your filing once it receives its copy of the 1099-R.