To become an alpha, you must create your own pack. You can name your pack, decide where you're living, decide who can join, and even make the decision of who is who in your pack (meaning if someone wants to be a warrior/medic/other pack rank, they must ask the alpha before requesting to join that usergroup).
And no, you cannot just randomly request to be an alpha and start a pack if you're travelling all by yourself and you know no one. You need followers, then you may put in a request to join this rank.