Cognitive learning theorists are people who come up with theories on learning as it goes on in our brain. (Cognitive : of or pertaining to the mental processes of perception, memory, judgment, and reasoning, as contrasted with emotional and volitional processes. )
They believe that learning is an internal process (i.e. it happens in our brain) in which information which we obtain from outside is converted and then integrated (Assimilated / becomes a part of) into one's thinking structure.
All that the sentence is trying to say is that we already have a structure of thinking built into our brain and learning happens by assimilating information that we get into the already existing structure and modifying it.
This is turn makes us more wise as we take into consideration the recently learnt information into account while taking decisions in life.