I only draw ss but I do pay interest on my home, and second mortgage and car. Can I use this

Unless you paid some tax, there is nothing from which to get a refund, so entering mortgage interest  or anything about a car will have no effect.   

It depends on your total income.  If you are single and made between $25,000 and $34,000 last year, up to 50% of your Social Security is taxable.  If you made more than $34,000, you'll pay taxes on up to 85% of your Social Security. When you enter all of your income, TurboTax will calculate the taxable portion of your Social Security.

Refer to the TurboTax articles Is my Social Security income taxable?, How does receiving Social Security affect my taxes? and When Does a Senior Citizen on Social Security Stop Filing Taxes?

Based on the information that you provided, the mortgage interest that you paid on your home will have no effect on your tax return. Deductions reduce the amount of income that you pay tax on and if you don't have to file a tax return, deductions have no impact.