Plug the bathtub and fill it with water. You are making this bath for yourself, so make sure that it is comfortable for you. Make the water as deep or as shallow as you like, and use a temperature that is not too hot and not too cold for you. Once you have filled the tub to your liking, turn the water off. Put the bath bomb in the water. As soon as the bath bomb enters the water, it will start to bubble and fizz. Over time, the bath bomb will start to break apart and dissolve, thus allowing all the beneficial oil, salt, and butter to be released into the bathwater.