Question

phrase beginning with a preposition

Answer 1

We should probably understand what a preposition is at first.
A preposition is a word that describes the relation between nouns and or pronouns.
A few examples would be: in, outside, near, far, on, beneath, with, ect

An example of a prepositional phrase is:
I put the bowl near the cat.
'Near the cat' is a prepositional phrase since near describes where the bowl is being put.

You can use this example to further create or scout prepositional phrases in a sentence.
(your question was a little ambiguous)