Combining simple sentences into a complex sentence can improve your writing. You are being asked to combine two simple sentences by making one sentence a subordinate relative clause (or dependent clause) that modifies or describes a noun in your independent clause. Looking at the first sentence, we can identify three nouns: comic, technique, and parody. The second sentences tells more about the comic so we will make this our subordinate clause and place it after the noun comic in the first sentence. An subordinate clause that describes is called an adjective clause and is usually introduced by a relative pronoun such as that, which, or who.
The new, improved sentence will read:
The comic, who does impressions of people, uses an old humor technique called parody.