"Where can I enter income from an irrevocable trust?"
If you have a K-1 that you received from a trust and need to enter it into your personal income tax return, you would enter that information in the Schedule K-1 section of the program.
NOTE that if you are using an Online version of the program, you will have to upgrade to TurboTax Premier or Self-Employed in order to enter information from a K-1 (your profile indicates you are using Online TurboTax Deluxe).