Do you publish first or after all changes are made?

I was watching the tutorial and it said to upload the power point presentation and then publish it.  Then make changes.  This doesn't make sense to me.  I would think that publish would be done after all of the changes have been made?

Or, is it you can do it either way - publish first, and make your changes.  Or, make your changes and then publish (which I am really hoping this is the case because this is how I did my first training class).