If you have a $10,000 capital loss carryover and capital gains of $12,000, the entire $10,000 capital loss carryover will be used to offset $10,000 of the capital gains. There will be no loss left to offset other income or to carry over to the next year.
As VolvoGirl said, the offset will happen automatically. All you do is enter your investment sales that produce the gains, and enter the capital loss carryover if TurboTax does not carry it over automatically.
