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:
White surrounds you. The sheer (しろ) amount of white is overwhelming.
Can you put the white dishes on the table?
Three out of seven stones were white.
The man was as white as snow, so he was named "Snow White."