You mean recharge? You can go to the Temple (Town Place -> Temple) and click one of the healing option. Or you can buy potions in the Magicks shop to heal yourself during a battle.
I suggest you also check the Newcomers Help Center. There's a few guide about the battle system and everything related to it there.
_________________
On semi-hiatus all the time during school year.
I'll reply to post whenever I can.
PM me if you need a quick answer.