You would need to use the TurboTax Business product to file Form 2553 Election by a Small Business Corporation. You could also file that Form separate from your tax return. It is used by a corporation or other eligible entity to elect to be treated as an S corporation. If you are an LLC, you would first need to apply to be treated as a corporation by filing Form 8832 Entity Classification Election before you used Form 2553 to apply for the S Corporation status. Once you prepare your S corporation return you will generate a schedule K-1 that you will use to enter your corporate income or loss on your personal tax return.
If you are a single member LLC, you may want to forgo the S corporation status, as you can enter your business income and expenses on your personal tax return as self-employment income. Then you wouldn't have to file a separate S corporation tax return which would be simpler and your income would have a similar tax treatment.
You may find this article helpful: LLC vs S Corp