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:
The reading for the 円 portion of this word is the same as a kanji you're learning in this level: 丸. That kanji means something really similar to this kanji. And guess what? They also share a reading. So, if you know that the reading of 丸 is まる then you'll also know that the reading for this word is まる!
Please line up the round plates on the desk.
The room with the round window is the princess's.
I’m afraid of the full moon.