Add the mini bombs or to your bath once it is full.
For best color result, let your bath bombs bloom for a minute or two before getting in.
For our kids, we add a few mini bombs to the water once it's about half full, so they bloom, and then give them more so they can enjoy playing with them in the colorful tub.
We recommend using at lease 12 mini bombs or 2 bomb cubes (the larger ones) to gain the skin softening benefits of the mini bombs, but feel free to use as many or as few as you want in a single bath.