qustion stands in de title

Well, go to the Clans tap at the top of the screen. Select the clan you want to join, and go to their forum. Their stands something as "recruiting center" or "do you want to join us/(clan name)?". READ THE FIRST POST FOR THE APP AND READ FURTHER FOR THE RULES OF THE CLAN. FOLLOW THEM OR YOU WILL PROBABLY BE DENIED.
Then, post the app which stands in the first post with your information. Then, the members vote and decide of your in or not.