Both Uses

initiate
in
The Perks of Being a Wallflower
(Edited)

I think this is the initiation for new cast members.
p. 111.5 *

initiation = ceremony (to accept new members)
And since she and her boyfriend never saw the show before, they were technically "virgins," which meant they would have to do all these embarrassing things before the show started to get "initiated."
p. 171.2

initiated = accepted someone's membership though a special procedure such as a ceremony and/or period of instruction and/or test

Definitions:

(1) (initiate as in: initiate discussions)
to cause (something) to begin
(2) (initiate as in: initiate into the art of drumming)
introduce to an activity or area of knowledge
(3) (initiate as in: initiate into the fraternity)
to accept someone's membership into an organization -- typically in a ceremony -- sometimes including a period of instruction and/or test
(4) (initiate as in: She is a new initiate.)
someone who has formally started in an organization, or been introduced to or attained some expertise in a particular field
(5) (meaning too rare to warrant focus)