I received 3921 for stock options exercised in 2015. Paid the taxes in my '15 tax return. Sold the cert in 2016 and received 1099-B. How do I reflect that in '16 return ?

I received Form 3921 i to reflect stock options exercised in Nov 2015 and a paid the taxes in my 2015 tax return (the information was also included on my W2) . I received a stock certificate and sold/surrendered for payment the certificate in early 2016. I received a 1099-B for the sale. How do I reflect that in my 2016 tax return ?  Thanks.