I tried finding the answer but I couldn't since I guess the game changed but is there a way you can use potions during a battle and how? Thanks.

You can use elixirs during battle! There is a red arrow icon in the lower right hand corner. You can click that or type the letter P to bring up your elixirs. :-)

There are two kinds of healing potions. The restore POTIONS cannot be used in battle, while the restore ELIXIRS can. If you put your mouse over the item and there's a This cannot be used in a battle in the description, it can't. Otherwise, it can.

During battle, there's a red arrow beside the satchel at the bottom right hand of the screen. Click on that to use the potion and click on the pet you want to use it on. You can only use healing potions every other turn.

In the festive zone, click manage, and then either 2, 3, or 4 depending on the type of potion you have. If you can click it, the box would be darkened. Then select the pet you want to use it on.

Hope that helps. ^-^