We need to complete several drills in order to unlock a skill.
How to complete drills?
Firstly, you need to pick a player.
Then click on the button at the bottom right corner to unlock the current skill. Skills have to be unlocked clock-wisely. You can use AP or Drill cards to complete drills.
Note: after a skill is unlocked, you can click on the icon to upgrade the level of this skill.
If the above answer can't help you solve the issue or didn't answer the question, you can reach our in-game customer service by clicking on "I NEED MORE HELP"