There are two ways.

* Upgrade. You can increase a card's stats by upgrading it. All you need to do is collect the necessary items shown on the card's upgrade info, spend a few Coins, and BOOM — upgrade complete. The number of upgrades per card is limited. When no more upgrades are available, fear not because there is also level up.

* Level up. When cards can no longer be upgraded, they can be leveled up. Leveling up a card improves various card stats simultaneously (Health and Attack, and maybe something else!). It also increases the amount of upgrades the card can have. Leveling up a card couldn't be easier: Just collect enough copies of the card, drop a few coins, and SHAZAM — card leveled up. All cards start at Level 1 and can be upgraded six times.