I agree with the others. If you are really unsure, just follow the instructions on the can.
We boil tap water, then put into a bottle, put the bottle into a mug of cold water and once it has cooled to a good temperature, add the powder. Of course, we only give one bottle per day, if that.
If your LO is exclusively bottle fed, you could always make a jug of formula each morning, keep it in the fridge, and then fill the bottles as needed and warm to room temperature.
I have also heard that after your baby is 4 months old, it is okay to use water from the tap instead of boiling it. I don't think I am ready for that though...