Skills are basic abilities that each Job Class has. Each Job Class has different Skills.
You can learn Skill and get it for the first time after obtaining Base Level 2 and Job Level 1. To be able to attach Skill to Hero, you must increase Hero's Base Level to a certain level.
Activate the Skill by "Select the Skill you want to use, put the Skill you choose into the Skill Slot (Icon with a plus sign) by touching the Icon, then the skill you have selected will be installed on the Skill Menu".
Currently the Skill is active and can be used in the fight.