how do file the sale of land?

You will report the sale in the Investment section:

• Select Federal Taxes 
• Go to Wages & Income 
• Scroll down to Investment Income 
• Select Stocks, Mutual Funds, Bonds, Other.
• Select Skip Import when asked about Brokerage Tax Documents. 
•  Then you'll be shown a list of various investment sales and you'll select "Other " Enter the name or person or financial Institution and continue. 
• You'll be taken to the screen that says To select the type of Investment. 

Enter the amount of gross proceed as it is on form 1099-S then add the deductions/expenses to the cost basis of the land.

Deductible Expenses:

1. Real estate commissions
2. Transfer tax
3. Legal fees
4. Advertising fees
5. Home inspection reports
6. Title insurance
7. Loan charges (points) or other fees paid on the buyer's behalf

For more information check: Capital gains and losses