Watching the video... let me add another remark:
You are some times referring to "the datasheet" which one has to look for clock configuration etc.
It is a bit different with stm32, more spread out into different documents, which are all rather huge, owing to the complexity of the beast.
The datasheet mostly contains information about what's in the chip, electrical characterikstics, pins etc.
Then there is a separate, huge, document: the reference manual.
This contains all the information on how to configure peripherals via setting register values, procedures, timings...
Those are found on the ST Micro page for the MCU, under the tab "design" or "design resources", where you'll also find a bunch of appnotes.
Then, there is a document, I think programming manual (like PM0056 for your puppy ), which is more general, for the e.g. M3 core of the processor.