One major trait of the Gothic novel is that its aim is to paint the world in its fallen, immoral state. The Gothic novel uses elements of "plot, setting, characterization, and theme" to paint the world as a "fallen world" (University of California at Davis, "The Gothic Novel"). As we are limited in space, below are a few ideas to help get you started.
The setting in particular is used to portray the world in its fallen state. The setting will be used to create an "atmosphere of horror and dread" ("The Gothic Novel"). To create the horrific atmosphere, the setting will portray the world in a "decaying" state by using images of darkness, coldness, and even images of bones, tombstones, or other elements of a cemetery. Emily Bronte's Wuthering Heights can be considered one example of a Gothic novel, and the novel's setting provides evidence of its Gothic elements. For example, the novel is set in a cold, dark estate in which all of its inhabitants are described as being miserable. The estate is even suspected of being haunted and is situated on a moor that's cold, expansive, and lonely.
A Gothic novel will also often contain specific characters, including a protagonist, a villain, and what can be called "the Wanderer" ("The Gothic Novel"). The protagonist in a Gothic novel is one who has fallen from his/her original state, or has "fallen from grace" ("The Gothic Novel"). We can look at Heathcliff in Wuthering Heights as an example of a Gothic protagonist. When first brought home as a foundling, he was cherished by his adopted father Mr. Earnshaw and developed a deep friendship with his adopted sister Catherine; however, his adopted brother Hindley became ragingly jealous of Heathcliff and, after Mr. Earnshaw died, Hindley stooped to humiliate Healthcliff, even treated him as a servant. We can call Heathcliff's humiliation his "fall from grace." What's more, the protagonist of a Gothic novel is often isolated, either "voluntarily or involuntarily." In Heathcliff's case, he first isolates himself through his rich plans to seek revenge against Hinley, and then, after his plans succeed, Heathcliff isolates himself further by staying by himself on the Wuthering Heights estate.
Beyond the protagonist, the villain is the one who torments the protagonist, just as Hinley tormented Healthcliff. Finally, the "Wanderer," while not in all Gothic novels, will roam "the earth in perpetual exile, usually a divine form of punishment" ("The Gothic Novel").