Clans are basically imaginary gathering places that have no purpose other than the stated. There is no clan function and the only way to join a clan is to contact someone who admits people into them on their profiles.
Aka, clans are pointless. Most appear to exist for the sole purpose of being thrown up on your about so you can state that you "belong" to something.
So depending on what clan you want to join, you'd first have to find someone in that clan, then contact them asking them to join. They then either accept, deny, or refer you to someone else who will do one of the former.
Actually, there will be a clan system in AG3, but no such system will be added to AG2. Until AG3 adds a clan system, you will simply have to do what Kasic said.
Well I'm the leader of a clan called the manly crew and I've seen enough of you in the forums to allow you to join
What Kassic said about them doing nothing isn't true about any clan from my experience anyway, the manly crew is a clan for any multiplayer game and not just games on armor games although that's all we usually talk about and stuff, so if you would like to joi the manly crew leave a comment on my profile and friend me
Me and a friend are founders of a clan and joining a clan I would think should be simple. If you want to join my clan or a clan in general just ask and they should let you in. Some clans (so I've heard) you need to be tested or something? Im not sure. For example if you want to join my clan just ask and you are in and it should be as simple as that.