Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. You didn't learn that reading with this kanji, so here's a mnemonic to help you:
Think about your favorite teacher. Now think about them teaching you the following: "Today I'm going to teach you about the ocean (おし)." It is big. Really big. Inside it are krakens, space aliens, and lost cities.
Here is where you continue the lesson in your head, making it the most ridiculous lesson about the ocean you've ever heard. Focus in on the ocean part, since that's the reading, always coming back to it.
Please teach me how to answer.
There aren't any "demon coaches" among people who teach Japanese on WaniKani, are there?
Good morning, class. Today I’m going to teach you about the dangers of eating eggplant.