As Instructional Designer you are required to have some insights into educational theories.
We do not like to put too much focus on theory, but we feel that this post covers the lot that you really need to understand and be able to apply in whatever or learning / training solution you will propose.
Hope you take something away from this post that you can apply in your own work.
https://www.growthengineering.co.uk/10-learning-theories-you-have-to-know/