I assume you used it in your sole proprietorship or single-member LLC. in TurboTax there an asset entry worksheet as you go through the schedule C entries specifically for vehicles. that's where it's entered.
if all use was business use then report it on the business. the gain will flow to form 4797 and from there to schedule 1. this will allow you to take a deduction for the business portion of expenses such as gas, insurance whatever. note that no depreciation is allowed because the vehicle was acquired and disposed of in the same year.
if part business and part personal use based on business miles to total miles you enter the full cost in the business section but only the portion of the sales price (insurance proceeds excluding license reimbursement) that's in the same ratio. also enter the mileage info. so say 2/3 business mileage. Turbotax will prorate the business cost to $10K you'll report sales proceeds of around $18K resulting in a business gain of $8K. this will work just like above.
Turbotax will not automatically do the personal portion. that goes on form 8949 as a short-term capital gain type C not reported on 1099-b you'll report the personal portion here which would be proceeds of about $9K and cost of $5K resulting in a gain of $4K
