Dialga had no prior experience in teaching other Pokémon, and its agreement to do so stemmed purely from a desire to satisfy its curiosity; it was always eager to try things it had never encountered before.
As for how to teach the most basic concepts to someone who neither understood nor knew the inner workings of time's power, Dialga's chosen method was to let them experience it firsthand.
Normally, there wouldn't be so much Memory Essence brought into reality. Although Memory Essence was a byproduct of the past revealing different futures, it was the best medium for a complete beginner taking their first steps in this domain.
Chapter 281