I just finished my 2020 return but I just realized that I forgot to put the medical expenses. how can I edit my return since I have submitted it one hour ago?

[SweetieJean]

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.

[DavidD66]

First wait to be sure your return is not rejected for some reason, in which case you can easily make changes to your return.  Next, you need to determine if there is any point to adding your medical expenses.  Medical expenses are deductible, if you itemize your deductions.  In order to get a deduction for medical expenses, they have to be greater than 7.5% of you Adjusted Gross Income, and then you can only deduct the amount in excess of the 7.5%.  For example, if your AGI is $100,000 you have $8,000 of medical expenses, only $500 is deductible (the amount above $7,500).