Jan 8th 2016, 9:59:36
Yep you must officially go through application (you should see link for their application in-game to that clan) process to join clan first. It is labeled as "Clan Homepage" in-game for that particular clans application. Once you have followed that link to apply to join clan and been accepted, that clan will than give you the password to join and tag up with that clan in-game.