Structures used in or by a business are assets that get reported as such. If this building is rental property then enter it in the Assets/Deprecation section which you will eventually come to as you work through the Rental & Royalty Income (SCH E) section of the program, the way it is designed and intended to be used.
If this is a business asset for your sole proprietorship or single member LLC reported on SCH C as a part of your personal 1040 tax return, then you'll enter it in the Business Assets section of the Business Income & Expenses (SCH C) part of the program which you will eventually come to if you are using the program the way it is designed and intended to be used.
