To upgrade a unit you will need power points and coins. After reaching level 30, you can buy special ability.
1. Open Team menu;
2. Choose a unit to upgrade;
3. Tap a button with a green arrow on it;
4. Insert the required number of power points by pressing and holding "+" button;
5. Tap "Upgrade".
Additionally, you can upgrade unit's stats by equipping it with items.
1. Open Team menu;
2. Choose a unit to upgrade;
3. Tap a button with a green arrow on it;
4. Insert the required number of power points by pressing and holding "+" button;
5. Tap "Upgrade".
Additionally, you can upgrade unit's stats by equipping it with items.