How do I amend my return and add on there someone can claim me as a dependent

Go to My Info and click your name.  Then go through the screens to the question that asks if someone else can claim you as a dependent.  Your answer needs to be YES.

If you already filed your return with the wrong answer, the person who can claim you will not be able to e-file claiming you this year even if you amend.  The only way they can file now is by mail  They can claim you---but it has to be on paper.  Their return must be printed and mailed.   They do not have to wait for you to amend.   Waiting will not help them.  They can mail their return when they have it ready.  Any attempt to e-file with your SSN on their return will be rejected by the IRS.

If you want to make changes to a tax return that has already been submitted, you should follow these guidelines. 

• You must first wait until the initial return is completely processed. 
• You will have to use the same TurboTax account that you used for the original tax return. 
• Once you begin your amendment, you'll see your original return.  
• The refund calculator will start new at $0 and only reflect the changes in the refund or tax due 
• Only make changes to the areas of your return that need amending. 
• You have three years from the date you filed your return or two years after you paid the tax due (whichever is later) to file an amendment 

Follow the instructions. 

Amend TurboTax Online