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:
Long ago, in a galaxy far away, a bunch of prequel movies were ruined by a single character. "Heesa (ひさ) the best character!" you hear. Oh no. Heesa here. Get out before Jar Jar Binks gets you! Keep him in the past!
It’s been long since I stopped eating bacon.
Japanese people have taken peace for granted for so long that they probably can't understand it anymore.
He ate a raw goldfish and has been dead for a long time now.