1) To PM is to private message someone. If you click on someone's name, it will say "send a Private Message to {insert name}"
2) To join a clan, you must be a member for one month and have 50 posts. You take a test and according to the results, you are placed in the Farore(Clan of courage), Nayru (Clan of wisdom) or Din (Clan of power) clan. But you shouldn't worry about that until next month. ^_^
(More information can be found in the FAQ on clans.)
3) try not to double post. It's much easier to edit your last post.