How am I supposed to go into the Mag Pit and choose which characters I want to play, when it keeps telling me I need an authorized password?!?!

You're not. The question 'which characters are you interested in playing' is on the application form which I gave you in the other 'Help' thread (link here, first post, scroll down, third question on the form, also quoted in your last thread). The password only gets given out if you're accepted and then we decide which characters to give you. :)