Navigate the site, find the ask the leaders section. Ask a KoG lader to help you out. Or the Ask a Generals part of the site or the ask a Captains part. Or just look through the clan list for KoG
Yes you do need an invite. but i never hurts to register on the forum then shoot a friend request to a KOG captain and getting to know them. If they they like they will probably invite you. besides it shows ambition. p.s just dont be pesky about it