I'm not sure if this is the right place to look. But I know TTX will already ask you about this so as to reduce or completely eliminate underpayment penalties.
If you'll take a look under the "Other Tax Situations" tab you'll see a selection for "Underpayment Penalties". Work that section through. I "think" you have to answer no to a screen that asks about W-2 income, before it will ask the questions you need it to ask.
