It takes at least a couple of weeks to receive a letter from the IRS. You may want to call them at 1-800-829-1040 and either ask for another letter or ask for details as to what you need to do.
You cannot redo your taxes once they have been filed. However, if the IRS requires that you change/add/remove/correct something on your tax return, you will have to file an Amendment.
Please refer to the link below on how to amend in Turbo Tax:
https://ttlc.intuit.com/questions/1894381-how-to-amend-change-or-correct-a-return-you-already-filed
