Well know first you're not allowed to make pack contests on the site. You can make ''applications'' on the forums if you want, or in your profile. Basically though you just pick a name, and start asking for people to join. Just be careful about who you ask and how. If you're polite and don't ask more than once, or whine if they say no, you shouldn't have too much trouble.

Joining one is similar. If you're curious about one, just ask the creator about it. Again though, be mature and don't whine if you're rejected. It's the creator's choice, not yours.