Severance pay should be reported (and entered) as part of your W-2 wages. Severance pay, including unused personal time payments, are fully taxable. This means that you should have received a W-2 that included these wages. If you received the severance in 2018, you'll get the W-2 next year. If you did not receive a W-2 that included all severance pay, contact your employer and request a corrected W-2.
If you have additional questions or details regarding this, please feel free to post in the comments for further clarification.
Note: More details on this topic can be found in the information below.
Self-Employment-Taxes/10-Tax-Tips-for-the-Suddenly-Unemployed