You will report that in the same section that report stock and other investment sales.  :

• Type "Investment sales" in the search window and click Enter
• Click on "Jump to Investment income (gains and losses)"
• On the page with "Did you sell any investments in 2018?"  Answer Yes
• Answer No to "Did you get a 1099-B..."
• On the "Choose the type of investment you sold" Indicate "Land"
• The interview will walk you through entering the details of the sale

If it was personal property (not bought for investment, not used for business or rental) be sure to indicate "Personal Use Only" on the "Any Business or Rental Use?" page