Your pass is your ticket. So for travel within Switzerland on normal public transit there is nothing you need to do. You do not need tickets. Just show up, board a train/tram/bus, and travel.
For the Jungfraujoch I would not book in advance. Only buy that ticket once you are here once you know the weather. That applies to all mountain railways.
The GA is a domestic product, and the Jungfraujoch railways is one of those cases where the GA reduction is not the same as the Swiss Travel Pass reduction.