How do we get acquainted with the concept of morality?

We get acquainted with the idea in the form of a need for a role model as we grow up. We look at different characters around us and look for specific traits and principles of behavior that we admire, that make us feel uplifted, that give us a sense of self esteem and enjoyment in living.

Practically, emulating these traits leads to achievement and enjoyment of our values: of the things we pursue, enjoy and need: like friends, hobbies and other productive activities (like cleaning our room, or building airplane models, or painting).

Existentially, the purpose of morality and the reason men need it is because they need guidance how to live: How to survive, and how to achieve things that improve their lives.
However, a man growing up gets acquainted with the need of morality through a feeling of admiration for role models - more so than through the need for a specific course of action to achieve some value.

The reason is that someone else's personality concretizes for us the principles of behavior. It allows us to take a step back from some specific action, to look at the underlying principles that guide the hero's behavior. Like being tough and brave, direct, independent, powerful, etc', vs. telling the truth in some particular instance, or a one time instance of managing to overcome fear of spiders to whack one to a mush. 

A nice example to illustrate this, is the T.V show Survivorman. Survivorman is, I am not ashamed to say - my hero. He goes out to the wild, for 7 days, with very little equipment - to survive on his own: on his wits and strength of character. 

Nothing illustrates better than that the significance of the right personality (which means, the right morality) for a man's survival. 
In nature, he faces so many difficulties, that if he did not have the right spirit - he would surely die. 
He needs to cope with cold, rain and hunger, he needs to have the strength to go and look for food, and think how to build a shelter after 3 days of no eating. He needs to find the strength within him to continue thinking of ways to catch food or heal his worsening injury under exhaustion, and he needs to be optimistic that he can find his way out of a jungle after a night of sleeping on spiders, crawling scorpions and killer ants, after walking in the jungle for 2 days without water and thinking he may not find his way back in time. He needs to be able to enjoy the beauty of the jungle or play his harmonica to uplift his spirit when everything seems to be going bad. 

What he needs is strength of character, optimism, rationality under pressure, being action-oriented and enjoyment-oriented and not trouble-oriented, determined, and brave. 

He needs a moral ideal to literally survive, and he needs to be that ideal. 

He needs certain personality traits (which are essentially principles of behavior, or virtues).

He needs something that takes all the specific actions required for survival in various situations, and abstract the underlying principles out of them.

When we grow up, this is what we respond to - the abstract principles embodied in the personality of our role model.
Even though we may not see the connection between that personality and the achievement of our values - the connection is there, existentially, and in our subconscious.