After you file

Yes.

If you have not yet filed your return, you can make the change in the My Info section of the program. 

1. Select Edit to the right of your name. 
2. Scroll down to Section 3 and change you answer to no under Someone else can claim me as a dependent on their tax return

If you have already filed your tax returns and they have been accepted, you will need to file an amended tax return.  I have included instructions on how to prepare an amendment below.

Amend return