I ran the bath for you.
You already learned the word 沸く which means "to boil" or "to grow hot" but this is when you are the one heating the water. It still means to boil or to heat. But remember that you're the one who is doing the heating.
Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. You already learned this reading when you learned 沸く, so you should be able to read this word as well.