Since this word is made up of a single kanji, it probably uses the kun'yomi reading. You did not learn this reading, so here's a mnemonic to help you to remember:
A chicken is a 庭 (garden) 鳥 (bird) (にわとり). It's a bird that you keep in your garden, after all!
The chick I raised became a chicken.
My neighbor's chickens wake me up every morning.
Am I right about this chicken being a rooster?