Should I categorize my notes on this slideshow thematically?
That would definitely be a good idea, as that is often a good way to organize reference material! But I would recommend to do whatever works best for you, but some sort of period/thematic chart will probably be very helpful!
how should I do that?
I would make a table with periods on one axis, and then different themes on the other axis (political, social, economic), and then filling in the boxes with vocab or themes that you can use for reference.