Prepositions link (join) two words to add meaning/information to a sentence. Use them whenever needed; do not be concerned about using too many. You can get the idea from these prepositional phrases (parts of a sentence):
(Concrete is) -- composed OF sand, rock, and cement.
(We might) -- die OF starvation.
(I am) -- good AT swimming.
(She is) -- married TO a Korean man.
(Some people are) -- afraid OF snakes.
(He was) -- pleased WITH his appearance, dressed IN a suit consisting OF shirt, slacks and vest.