I have already filed a 1120-s for my s-corporation and had a loss this year. Can I write this off on my 1040 and where do I place that on my turbotax form?

The S Corporation should have provided you with a Schedule K-1.  The Schedule K-1 is entered on your personal tax return, Form 1040.

To enter a Schedule K-1

• Click on Federal Taxes (Personal using Home and Business)
• Click on Wages and Income (Personal Income using Home and Business)
• Click on I'll choose what I work on (if shown)
• Scroll down to Business Items (Business Investment and Estate/Trust Income using Home and Business)
• On Schedule K-1, click on the start or update button

Or enter k-1 in the Search box located in the upper right of the program screen. Click on Jump to k-1

Note that in order to deduct your S Corp loss, you must have "basis".  See the Basis Limitations section of the Instructions for Form 1120S Schedule K-1 at this link and the IRS website on S Corporation Stock and Debt Basis at this link for guidance on calculating your shareholder stock and debt basis.

@piperjanesadie