How do I apply to a clan?

I really dont understand how it works these days, back 5 years ago when I used to play active every clanpage on the forum had a "Apply" button, but now I just don't get it.

Can someone please explain this too me?

about 5 years ago you could apply on the site
now you can apply ingame at the right corner u can see a 'shield' with a star in it thats for clans

Via in-game.