I checked and I have the correct one (I think). The tutorial said I should stock up on them so I'm assuming I can use them, as the ones I have don't say they can't be used in battle. They're in my inventory btu I can't see them in my pack when I'm fighting.

Press "P" or click on the button that's the big red arrow next to your inventory button. This brings up the "Manage Party" window. From there hit "Use Item". Then you can select one of the items to use on a party member.

There are 2 different types of bottles, one is a potion (vertical rectangular shape), and the other is a Elixir (triangular shaped). Potions can't be used in the middle of battle, and can only be used through your actual inventory (so you could open a new tab on your computer and use them there). Elixirs can be used in the middle of battle, and are found under the use item button in your Manage Party. Note, you can only access this though if you are in a battle, otherwise it will be gray and unclickable.