I was able to set the high/low temperature alerts easily along with the time when I first took it out of the package, and I haven't had to change anything since. I did keep the instructions, though because I don't think I would remember how to do it after a battery change or anything like that.
It's so easy to use. I set everything up one time, and I keep it on my bathroom counter until I need it. Then I just drop it in the bathwater while I'm filling the tub, and I keep an eye on it while I'm filling. Then I make sure to swish the bathwater around to make sure it's well mixed and give it a minute to make sure there are no hot spots (we have a big bathtub, and I get in with my infant for her bath so much easier and she can "swim" which makes it more fun for her and stays warmer longer). The red light flashes and it beeps if the water is too warm, and it's a green flash (I think it's green) if it's too cool which I haven't had that happen yet. It automatically senses when it hits the water and starts a timer, which is awesome if you want to limit the amount of time your child stays in the bathwater (some say to limit to like 5 minutes, which is crazy to me if baby is warm enough and having fun but to each their own), and it automatically stop the timer and goes back to the clock function when you take it out of the water. So if you are like me and have it in the