Since this word is made up of a single kanji, it should use the kun'yomi reading. You haven't learned this reading yet though, so here's a mnemonic to help you:
You look down and you've sprouted a tail! You're so shocked that all you can say is "Oh. (お) Oh okay..." This your life now. A life with a tail.
Koichi can look at a fish's tail and tell you what kind it is based on that alone.
Without tails, birds would have difficulty landing.
Why do you think the custom of shortening dog’s tails started?