If you're setting up a Rental Property, in the Assets section, you'll enter a Cost Basis for the building and land value together, then enter a land value (usually 10-20% of total value, check your Assessor's Statement for the ratio).
You could then add Assets for each of the adjoining lots, especially if you think you may be using/selling them separately in the future. There's a separate Asset category for Land.
You'll need to assign a Cost Basis to each; however, since land doesn't depreciate, you don't get a yearly depreciation expense, but land improvements such as roads, sidewalks or landscaping may be written off over periods of 10, 15 or 20 years depending on the specific nature of the asset.
Here's more info on Depreciation of Business Assets.
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