TurboTax will guide you through the amending process. You must wait until the 1040X is available before you can start it. It will be available later in February.
DO NOT change your original return until you start the amended return. If you already changed it, change it back to the way it was when you originally filed it. Wait until you get the refund from your original return before you start the amended return.
See these instructions for help: https://ttlc.intuit.com/questions/1894381-how-to-amend-change-or-correct-a-return-you-already-filed
