Before you can partake in any Clan action, you must rebuild the Clan Castle!
On your map, you'll find an old, abandoned Clan Castle. Tap on it and select "Rebuild" - it will cost you 10,000 in Gold. To be able to hold this much Gold, you must be Town Hall level 3 and have your storages updated.
Once the Clan Castle has been rebuilt, tap on "Clan" for the option to either search for an existing Clan to join, or create your very own!
Searching for a Clan
To begin with, go to My Profile and have "Clan Invites" enabled as this will recommend you to Clan Leaders who are recruiting new Clanmates. Once this is done, check out the Suggested Clans on Join Clan tab, where Clans with a decent amount of activity are shown. If you're looking for something more particular, you can insert search words or use "Filters" to reveal the advanced search.
War Frequency relates to how often the Clan participates in Clan Wars.
Clan location is freely set by Clan Leaders but often represents where at least most of the Clan members are from.
Minimum Clan points is an indication of how active the members are in Multiplayer matches and Versus Battles, as it is counted based on their trophies. The higher the Clan points, the higher-level players the members likely are.
Minimum Clan level refers to the amount of experience the Clan has accumulated through Clan Wars.
You can also use labels to find the Clans that best matches your play style. Go to My Profile and select up to three labels that describe you. These labels will be taken in to account when you're looking for a Clan, and also when Clans are looking for you. You can also filter the Suggested Clans list based on labels.