How can I offset my gambling winnings with my loses?

Gambling winnings are not directly offset against your losses.  Your gambling winnings are included in income in the full amount.  Your losses are only usable if (1) you itemize your deductions; and (2) you can only use gambling losses up to the amount of winnings. So if you have $1,000 in winnings and $2,000 in losses, you can only use $1,000 in losses on your return and only if you itemize your deductions.  

Enter in your gambling winnings in the Less Common income section and you will then be asked about your losses later in this section.

Yes, you can enter the gambling winnings and losses (up to the amount of winnings) on your federal return

Gambling losses  get entered into TurboTax after you first enter your gambling winnings, following these steps:

• In your return, select Federal Taxes
• Click on Wages & Income
• On "Your income" page click on "Show more" for Less Common Income
• Click on "Start" button for Gambling Winnings

The interview will ask whether you have any gambling winnings, and will then ask you about gambling losses.