Science is organized knowledge. Wisdom is organized life.

-Immanuel Kant

How do we achieve what is good?

There are no rules for applying knowledge to a given situation you are experiencing here and now. The "right reason" can vary from one occasion to another. Proving one view against another is not possible by argument alone. If you lack insight into what is good, I might not be able to convince you of the goodness of being kind. What is good or bad can also be interpreted differently in different cultures.
It is not possible to make generalizations about right or wrong, good vs. bad that would be true in all cases.
Even the ancient Greek philosophers agreed that rules and principles rarely apply clearly to real-life situations and moral knowledge can only be acquired through experience.

So if practical wisdom cannot be taught, how do you acquire it?

The path to practical wisdom starts with the right mindset or some might call it intention, others virtue. This refers to a valued quality of a human being. In the Greco-roman traditions, they prized four qualities, calling it the 4 cardinal virtues: temperance, prudence, courage, justice. In Christian traditions, there is humility, kindness, temperance, chastity, patience, charity and diligence. In Buddhism as outlined in the "Noble Eightfold Path" there is Right view, Right Mindfulness, Rich Concentration. In modern daily life, we might consider the right mindset or virtues to be any number of behaviors which are inherently beneficial to oneself and society. What appears good to someone depends on their character traits.

"Practical wisdom is the moral will to do what is right and the skill to figure out what the right thing is."

Because we are good we aim for a good life and we have a conception of what this involves. Pick any one or any number of the human qualities or traits we deem to be good.

If we go along with the presumption, that we can have good dispositions from birth, you can act according to your good nature but you still need to comprehend the nature of your actions. Without comprehension, you might be misled by others to be "good" for the wrong reasons or at the wrong time, which would not lead you to practical wisdom.

The right mindset has to be paired with reasoning and comprehension. We become good and practically wise as we gain more experiences in life.

Wisdom is not a product of schooling but of the lifelong attempt to acquire it.

-Albert Einstein