You should have received a 1099-R if you received a distribution from a retirement account. Use the instructions in the link below. The taxability of your form depends on the type of plan it is and the code in Box 7. Enter your 1099-R exactly as it appears. Then, carefully answer the follow-up questions.
With plans such as Roth IRAs, the income was already taxed during contribution, so it won't be taxed now.