@ObsidianMage

Vamps Guide sums up a lot about potions

I'll just repeat the basics of that guide

-You can attach them to a hoarding pixpet, 3 at most
-They must be the same color as the pixpet's color group or neutral
-For now, all potions are by cooking. Super potions on the other hand aren't the same as your typical potions and are traded with SPC.

@ObsidianMage

Edit: Haha whoops, ninja'd!

Welcome to the site! :D

To use hoard potions, you want to go to your pet's hoard page (Pixpet Inventory > View Details/Hoarding Status) and there are slots where you can add potions before sending your pet on a hoard. You can add up to three different ones, and they can only be added while your pet isn't on a hoard and isn't recovering.

To use Super Potions, generally they're used wherever they're needed. For example, an Instant Cook Super Potion can be used at any cooking station--you'll see a button that says "Cook Instantly" or along those lines. The majority of Super Potions are used on a pet's hoard page; you'll see various buttons like"Instant Recover/ Instant Hoard Return, Change Name, Change Gender", etc. That's where Super Potions are used! :)