If you exercised and held NQSOs in 2018, and did not sell them in 2018, then there is nothing to report, other than the income that is already included in box 1 of your W-2. If you sold in 2019, you will report the sale then. Your cost basis will be the amount you paid plus any compensation added to your W-2 in 2018 due to the difference between the option strike price and the share price at the time of exercise.
If you exercised and held NQSOs in 2018, and did not sell them in 2018, then there is nothing to report, other than the income that is already included in box 1 of your W-2. If you sold in 2019, you will report the sale then. Your cost basis will be the amount you paid plus any compensation added to your W-2 in 2018 due to the difference between the option strike price and the share price at the time of exercise.
Assume the same question, but now I just sold the shares I held for 1 year. How do you get to the interview where I enter this sale? The NQSO interviews only asks if you've done a same day sale.
Enter your 1099-B and adjust the basis to include the amount added to your w2 plus any sales of expense. See Where do I enter a 1099-B?