How does the release of a new character work? (Tom Clancy's Rainbow Six: Siege)

Started playing recently, in the area of a month and a half ago, friends said that I can not immediately buy arun, because there is a period of 2 weeks, when you can not buy a new opera, and I saved 25k and was very much waiting for it ... They said that whether the battlepass opens the character to buy, when you get to him on the battlepass, or opens it for the game.
In any case, I want to ask people who have caught more than one season, about such subtleties of the release of new characters and ask to describe how I get a new operative in not 2 weeks.