These little video tours/tutorials were actually made for people viewing and ordering their kids' school portraits, so there are a lot of references to things that don't apply to the wedding galleries. However, there might be a few things that will be helpful for you, especially regarding:
Initial access to the gallery
I will try to replace these videos with more universal ones that apply to all situations in the near future. But until then, these should hopefully help with enough info that you can glean to answer most questions about getting around and ordering from your galleries. :)
To view a video at full-screen, hover over the playing video to make the little toobar appear at the bottom, then click the full-screen icon (currently looks like a little square with an arrow pointing diagonally up and to the right) on the far right of that bottom toolbar.