Since this word is made up of a single kanji, it should use the kun'yomi reading. When learning the kanji, you didn't learn that reading, so here's a mnemonic to help you with this word:

You have your body. It's nice - looking good! What would really mess up your body? It would be a car raider (からだ). I'm talking about a dude who is a raider of some kind driving a car. If he runs into your body, you're done for, so watch out for the car raider.

Of course, this mnemonic is only meant to get you close to the reading. Hopefully it is close enough to get you to the actual reading, からだ.