This guide will let you know where to Brew Potions in Hogwarts Legacy.
There are two different locations to do so. For the first one, you will need to follow the story and you will get a message from Professor sharp that you need to attend your potions class. So make your way to the potion station and you can make potions and herbs there.
It is recommended to follow the main story and get to the point where you can unlock the room of requirement. As you do each main chapter, you will get a message from a small house elf called Deke telling you how to unlock the room requirement. After unlocking it, you will have everything in one place and you can also brew potions there.