Estimated tax alternative

I am a retired federal employee with invested savings. This year I had a lot of capitol gains, resulting in a high tax bill and a penalty. TurboTax is suggesting that I pay estimated taxes to prevent this from happening next year. Can I submit a form or somehow increase the amount that is withheld from my pension check each month? I'd rather do that instead of deal with quarterly estimated tax payments. Can I do this through TurboTax?