To use alchemy, you'll need a Mortar and Pestle (found in Twigroot Forest), and you'll need some
combination of the six ingredients available in the game:
Then to create a potion (or a bomb), you'll need to have one of your characters equip the Mortar
and Pestle, then right click on it, and then select up to three of the ingredients. If you use a
valid recipe, then you'll end up with a potion (or bomb).
Having an Alchemist in your party isn't required, but Alchemists will
"grow" any ingredients they have in their inventory, making them useful for alchemy, especially
for obtaining Crystal Flowers.