Level 2

After you file

The IRS sent me a letter saying that I owed money back because I overstated my mortgage interest.  I paid it because I had just moved and couldn't get to anything and didn't want to get fined.  I was finally able to get a copy of the mortgage interest form and my original filing was correct.  Do I do a 1040X and if so, how do I fill out the columns?  Not sure what is now the original and what was corrected and what it should be!  Help!!