It doesn't matter that you received two 1099-S forms, just add the values together.  There is not an actual 1099-S entry form in TurboTax.  You can enter the sale of your home (and vacant lot) using these steps:

1. On the Wages & Income screen, in the Less Common Income section, click the Start box next to Sale of Home.
2. On the Sale of Your Main Home screen, select Yes. 
3. On the Sold a Home screen, note the information you'll need to answer and click Continue.
4. Continue through the screens, answering the interview questions.  As you go through the screens, you can get additional help by clicking on the blue links that appear. [See screenshot #1 below.]
5. On the Tell Us About the Purchase of Your Home screen, we recommend you click on the Easy Guide box to help you calculate the Adjusted Cost Basis of your home.  [See screenshot #2.]