One way to think about this is to think about what a devoutly Catholic youth might feel like if they attended a Christmas or Easter Mass celebrated by the Pope. This is what the Nuremberg Rally would likely have felt like to a member of the Hitler Youth.
The Nuremberg Rallies were huge propaganda events for the Nazi Party. They were stage managed to look very impressive and to make Hitler look as impressive as possible. The rallies eventually came to have as many as half a million people in attendance.
To describe it from the point of view of a member of the Hitler Youth, then, talk about how immense the crowds are. Talk about how you all idolize Hitler and how thrilling it is to have half a million people chanting in unison. Maybe talk about the huge banners bathed in spotlights or the "cathedral of light" formed by the spotlights at some rallies. Make it all sound like a holy experience because that is what it would have felt like to a true believer.
If you want to get some idea of how this all would have looked, you might want to watch video of "The Triumph of the Will" a movie by Leni Riefenstahl. You can watch it here, though a more high definition picture would be much more impressive.