If your return has been accepted, then you will need to amend your tax return by following the instructions in the FAQ article below. Please note: the person who is supposed to claim you as a dependent will need to file by mail.
Once you are in your amended return, take the following steps to change your personal exemption.
1) Go to Personal Info > Personal Info Summary > and click Edit to the right of your name.
2) Scroll down to Question 3 - Someone else can claim me on their tax return.
a. If you select yes – someone can claim you
b. If you select no - you claim yourself