Where do I enter Payroll taxes and wages that I have paid as an employer in TurboTax?

Yes, the wages and taxes that your company paid are considered a business expense.  They will need to be entered as wages and as taxes paid, no matter what type of entity your business is.  

What can I write off as a business expense?

Employees Gross Wages goes on Schedule C line 26 Wages
The employer portion of taxes goes on line 23 Taxes and Licenses

If Employee Expenses doesn't show up in the list you need to go back to the Business Profile section and click Edit by Has Employees and change it to yes.  What version are you using?  And Online or Desktop program?

Go to Business tab- then Continue
Choose Explore on my own or I'll choose what to work on (if it comes up)

Then…..
Business Income and Expenses - Click the Start or Update button

You should see the Business Summary page that lists your businesses, (right below the list you can Add Another Business)

Then click EDIT by the business name and the next screen should be a list of topics,
Business Profile, Income, Inventory/Cost of Goods Sold, Expenses, Assets, and Final Details last.

Click Start or Update by Business Profile
Then Click Edit by Has Employees and change it to yes.