You should always level your units to their current level caps when possible. This ensures that your unit can perform its best during battles. Units earn EXP and can level from battling, but you can also increase their EXP and raise their level by using Apples.
How to Use Apples
- Tap on Menu (located on top right)
- Tap on Units
- Choose a unit
- Tap on Enhance Unit
- Tap on an Apple and the unit will gain EXP immediately.