This is a user to user forum and nobody here knows your tax situation, can see your income tax return or your computer screen. You also haven't disclosed the amount of the capital gain nor the nature, (long term, short term), of the capital gain.
Short term capital gains get tax like "ordinary" income such as wages, interest income and the like, so if the capital gain is short term, it will get taxed if your total income requires that you file an income tax return.
Long term capital gains first get taxed at 0% if your total income does not exceed the upper income limit for the 2nd lowest tax bracket. But if the long term capital gain is of sufficient amount that you exceed that upper limit then the amount of LTCG above the limit is taxed at 15% and then at 20% in the highest tax brackets.
