Witam, Gruchen. When your manager asks you to cascade information, he wants you to pass it on to people at the level below you in the organisation, who can then pass it on to people at the level below them and so on.
Thus the 'cascading route' would be a list of the people (or departments) who receive the information and pass it on:
Jin receives the information from the manager and passes it on to Tom in department A, Dick in department B, and Harry in department C. Tom, Dick, and Harry each pass the information on to the people in their department, and those people pass it on to other people in other people in other departments, and so on.
The instructions say that this should all be laid out clearly, so that everyone knows who gets the information and to whom they should give it.
If this does not fit the context, please explain what still puzzles you and we will try to help.