form 6252 line 8

Line 8.—Enter the original cost and other expenses you incurred in buying the property. Add the cost of improvements, etc., and subtract any qualified electric vehicle credit, diesel-powered highway
vehicle credit, enhanced oil recovery credit, disabled access credit, or casualty losses previously allowed. For more details, get Pub. 551, Basis of Assets.

Not sure what you sold so I cannot give a more specific answer ... if this was a rental property and you had been depreciating it correctly then the sale would be handled in the Sch E asset section. 

If this information looks foreign to you then I highly recommend you seek local professional assistance or upgrade to the LIVE version of the online program.