We received a 1099-MISC for 4 days of RV lot rental (we stayed 48 days). Where can I enter the related expenses?

That depends on whether the 1099-Misc relates to a business that you own/operate, or whether it relates to a one-time event, something more akin to a hobby.   We need you to clarify the nature of your RV lot rental.  Do you rent the RV?  Or were you staying at the RV site?  It's not clear from your post why you received the 1099-Misc, and who gave it to you.

Notwithstanding the above questions, if this 1099-Misc relates to a one-time event, not an ongoing business, then you can report the income as other income.  You won't be able to deduct your expenses, but you will have to report the income.  If your activity were a business, you would be able to deduct your expenses as business expenses, thus reducing your taxable income.  Here are the steps to enter the 1099-Misc as other income:

1. To enter other income in TurboTax online, click on Wages & Income, 
2. scroll down the page to Less common income, click on the drop-down arrow and select Miscellaneous Income.  
3. From the list select Other reportable income and respond to the questions on the screens that follow.  

If you are using TurboTax CD/download, the process is similar.  After selecting the Wages & Income tab, scroll down the screen to Less Common Income, and select Miscellaneous Income.  Enter your information. 

If this 1099-Misc represents income earned in connection with your business, then the 1099-Misc gets entered in the Self-Employment section (TurboTax online) or in the Business Income section (TurboTax CD/download).   Both options will generate a Schedule C, Profit or Loss From Business and it is here that you will also enter your business expenses. 

@jhaddad1