You must wait to see if it is Accepted or Rejected first. If Rejected, you can add them and refile. If Accepted, come back at the end of the month when the 1040-X amended return form is ready here.
But note that only the amount of Medical that is in excess of 7.5% of AGI will count as a Federal itemized deduction, and your total eligible itemizeds must exceed the Standard deduction. You will also have to upgrade from TT Free to itemize. So unless your Medical is high relative to your income (or you have other itemized deductions), it may not benefit you for Federal. But State taxes may be different.
