Were do I amend my taxes to add a DBA business?

It depends.

You may not need to amend if your overall tax refund or amount due will not change.

Please see the attached link to determine whether you need to amend your return or not.

Do I need to amend?

If you determine you need to amend your return, please see the attached link for instructions on how to amend your return.  

How to amend my return?

If you need to the add the DBA to a self-employed business, once you start the amended return, you will be able to make the changes in the following section in the federal interview portion of the program.

1. Select Income & Expenses 
2. Select Self-employment income and expenses 
3. Proceed through the screens to enter your information regarding your business.