I have the Home & Business version so the lower versions are different and I don't know them very well. What's below Rental Properties? Isn't there Business Items?
You can just type Schedule C into the search bar at the top of your return and it should give you a JUMP TO link to go directly to it.
Or try going to Federal
Wages and Income,
Then scroll way down to Business Items
Business Income and Expenses - Click the Start or Update button
