Room temp or lukewarm water. If those are packets, it should be 4oz of water. Then pour the packet it and shake it.
Always test the water on the inside of your wrist if you ever heat up the water. If it hurts your skin, it’s too hot for baby.

I just went to their website and boiling the water is optional but if you do use boiling water it said to make sure you let it cool to room temperature before mixing in the formula.

I always used luke warm water or room temp. Never boiling or too cold.

I think all formula is used with cool or warm water ?