In magic, a potion is any liquid spell, be it an oil, tea, bath, lotion, etc. These potions are not all meant to be consumed, some contain items that can be poisonous, or not intended to be consumed in any situation. [example, rocks]
2. IF IT ISN'T TO BE CONSUMED, HOW DOES IT WORK?
In the case of a bath or lotion, you soak in it, visualizing the results the potion promises. [softer skin, less blemishes] Others you are suppose to inhale the fumes. With these it is similar to the baths, where as you inhale you visualize the intent. Third is to be used as a charm, to be burred, hidden, or worn. You keep it as a means to attract or dispel that which you made it for. [love, protection, luck]
3. DO I NEED A CAULDRON TO MAKE POTIONS?
While a cauldron is a nice addition, it is not needed. most are made on a stove top. Tea's can be made with a kettle, baths and are in the sink or tub. The one thing that would make everything easier would be a mortar and pistol, you can use the bottom of a pot to crush your herbs, but a mortar and pistol makes everything easier.
4. HOW SHOULD POTIONS BE STORED?
Depending on what type it is. Baths are dry, like sea salt and milk bases, which are added to the bath while it's drawn, and a chant said while pouring the dry mix into the water. For these, they should be kept in a dry place, in the bathroom is the logical place, in a jar with an airtight seal so no moisture form steam will get in. For tea's you can do something similar, mixing a large dry batch, stored in a jar, to be measured out when needed, and added to a cup of boiling water. Oils are trickier to make, but are stored in the same way, in a cool dark cupboard. All types though, tend to have a shelf life of 1 year.