Yes, you owe taxes for the difference between the Exercise price per share (block 3) and the Fair market value per share on exercise date (block 4) on Form 3921. To enter that information along with the associated dates and number of shares, go to Federal Taxes. Find "Wages and Income" and go down to "Investment Income" and click on "Show More." At the bottom of "Investment Income," you will find a section titled "ISO Exercise and Hold." Click on that and add purchase. It is straight forward from there. You will have to add another purchase for the second 3921 that you have. After you have entered both 3921's, click on Done.