There are two main rules to follow to use prepositions.
i. Preposition’s Choice: Certain prepositions must follow certain words and make the relationships between words in the sentences clear.
e.g. a. Able to
b. Capable of
c. Preoccupied with
d. Prohibited from
These prepositions must follow these words. It would be grammatically incorrect to say “able with” or “capable to”
ii. Preposition’s Position: Prepositions are followed by a noun and have an object, and hence they are not used at the end of a sentence. However, in certain cases the meaning of a sentence can change without the preposition at the end of the sentence.
e.g. “I turned the TV on.”
If you removed the “on” from the end of this sentence, it would change the meaning. Instead of switching on the set, one would be saying that one turned the TV itself.