No piece of income is taxed individually. All your income, including capital gains*, is added together at tax filing time. The tax is calculated on that total (after adjustments and deductions). Look at form 8949, if the sale is there, then it is included on your return. The capital gains tax rate is 0% for people in the 12% (or lower) tax bracket.
* A special worksheet (not a tax form) is used to calculate tax when you have capital gains.
