Before I file, I received some dividends on stock I own. I did not withdraw anything, just left it in the account. Do I need to add this to my taxes.

Wait until you get the tax forms from your broker.  

Yes, dividends are taxable whether you received a check or just left them in the account. For your installment sale, you would need to report the interest portion of the monthly payments as interest income. Since you sold the property at a loss, the sale itself should have been reported last year.