May I use definite article in front of abstract noun?
1.Creativity is a must in the present world.
2.The creativity of our boss has taken attention.
when and why I will use definite article?
It's pretty much the same rule for all nouns, abstract or concrete. When referring to a general concept, either use no article or the indefinite article. When referring to a specific or known instance of that concept, use the definite article. This helps your audience know which you are talking about.
Example using a concrete plural noun:
Pencils can be sharpened with a pencil sharpener, but the pencils used for drawing should be sharpened with a razor blade or penknife.
Same for abstract nouns:
Integrity is normally a vital character trait for anyone in a position of trust, but the integrity of this well-known character seems deeply flawed, or even nonexistent.