First you need to wait until the original return is processed and you get your refund.
Once you get your refund you will know that IRS has finished processing it and then you will ge back in and do the amended return adding the SSA-1099 (and anything else that may have been missed).
Note: An amended return has to be paper filed. Also the amended returns for 2017 will not be available until around mid-February 2018.
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