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:
Imagine someone riding a horse. Who is that person? It's Uma (うま) Thurman, the famous actress.
Is it okay to give that horse carrots and apples?
My horse has overcome yet another difficulty.
I find it unreasonably funny when old people fall off of horses one after another.