In TurboTax Online, you will need TurboTax Self Employed to make this entry. 

To enter 179 deductions, please first make sure your assets are eligible by reviewing  these guidelines.

Then, take the following steps to enter them:

1. Click on My Account in the blue bar at the top
2. Click on Tools
3. Click on Topic Search
4. Search for Schedule C and then click on Go
5. From this screen, you will see one of two things:

Here's the business info we have so far - Click Edit next to your business name. Then, scroll to the Business Assets section and click Start/Revisit/Update. You'll see Any Large Purchases (Depreciable Assets)? Answer yes. Answer Did you buy any items for any business, rental property and/or farm that cost $2,500 or less in 2016? Answer Did you make improvements to a building you used for this business in 2016? You may see a few other screens, but when asked Do you have any items for this business that aren't covered by your elections? you would select Yes. You will answer questions about your assets in general and be asked to enter the cost and date purchased. Finally, you will see a screen titled How Do You Want to Deduct this Item? (see screenshot below). On this screen you will categorize the asset as a 179 deduction.

Here's your work summary - Click Edit next to your business name. On the next screen, click the button to Add expenses for this work. Next, you will see Add expenses manually. Select the button for Assets: Larger purchases (usually more than $200), such as computers, furniture, or equipment. You will answer questions about your assets in general and be asked to enter the cost and date purchased. Finally, you will see a screen titled How Do You Want to Deduct this Item? (see screenshot below). On this screen you will categorize the asset as a 179 deduction.

If I can be of more help, please comment back.