If you purchased your inventory in 2017, you can deduct  the cost of of your inventory purchased less any used for personal purposes.  Any goods or inventory purchased in earlier years were probably already claimed on previous tax returns, so you would not expense them a second time. What are you going to do with the remaining Inventory? If you keep it around and then sell it,  you would have to report the income in the (later) year of the sale probably as miscellaneous income.

When completing your schedule C Turbo Tax will ask you your business start date and close date and will walk you through completing your schedule C.