To join a clan, simply talk to any of the clan leaders and pick [Join].
Because you need guildleaders to WoE, clansmen cannot participate in WoE. So pick a character you don't WoE with if you want to check out a clan.
Clan chat options has been added to the chat box. The /cl command works like % for party chat and $ for guild chat. (Not sure why kRO did that for clans instead of picking an unused symbol.) Clan chat shows up in pink text, so be careful you don't mistaken it for party chat.
Don't think fellow clansmen show up on the world map; will need more testing to see.
Feel free to post questions and feedback here.
EDIT: If you're inactive for 2 weeks straight, you will be automatically kicked from the clan. Judging from the kRO screenshots I've seen, there's limited space in each clan so this makes sense. Although there should be an ability to increase membership, but oh well. Campitor confirmed: maximum capacity for each clan is 500 characters.
EDIT3: The clan quests and certificates were unfortunately part of a separate update. From the looks of things, we only got the intro update for this system.
Edited by ZeroTigress, 26 March 2018 - 01:59 PM.