Received a 1099-S for proceeds of a sale of a second home. What form do I use to report it? and where do I record expenses etc?

You will report the sale of a second residence in TurboTax Online under Wages and Income, in the Investments section.

1. Scroll down the screen until you come to the section “Investment Income”
2. Choose “Stocks, Mutual Funds, Bonds, Other” and select “start’ or click "Add Investment" if you have already worked on this section
3. Continue. When you see a list of brokerages for import, click Enter a Different Way
4. The next screen has a list of investment types. Click on Other / 1099-S, which includes second homes

See this thread for further discussion on how to report the information on the sale so that TurboTax can calculate the gain. No deduction would be allowed for a loss on the sale of a personally used second residence.