Since this word is made up of a single kanji, it probably uses the kun'yomi reading. You did not learn this reading, so here's a mnemonic to help you to remember: You jump on a wave and ride around the world on it. It doesn't drop you off anywhere, until you reach a certain location: Vietnam (なみ). You jump off the wave and look at Vietnam. Imagine the most Vietnamese things you can think of to help you to make this wave-Vietnam association.
Today's waves are very high, aren't they?
OMG! Koichi has been swallowed by a wave!
The rocking of the waves to and fro feels good.