I have no clue from what you've given which Gothic novel you might be reading; however, there are some common elements among most novels of this genre. You ask about three of them, so here goes:
Language - The language is typically dark and ominous, as if something bad is always about to happen. There may be elements of mystery and suspense, often heightened by the setting (mentioned below). There is not much joy or delight in a truly Gothic novel. Think Edgar Allan Poe.
Setting - Marked with death and decay; morbid and dark; foreboding and frightening. The buildings are generally tall and show signs of decay and "oldness"--and of course they have the expected winding staircases, attics, secret passageways, and basements/dungeons. Cemeteries and other kind of "creepy" places are typical stops in a Gothic novel.
Atmosphere - This is created by the both of the other things just mentioned. How does an author create a particular atmosphere but by his words and his settings. Add characters and plot (which you did not mention) and that's all there is.
A completely Gothic novel would be a pretty dismal read, I think. Instead, we find Gothic elements throughout many works over the years.
The post above answers the first part of your question. In chapter 5, the monster comes to life. Victor freaks out and runs into the street. He later meets his friend Clerval. They go back to Victor’s apartment, where Victor becomes ill after months and months of working on his creation. This chapter is important because it is a turning point. Victor finally sees that what he has created is very far away from the purpose of science. The gothic atmosphere of the novel increases now because the monster’s presence is always looming before Victor, whether he is actually there or just present in Victor’s fears. From this point on, the threat of the monster is always with Victor. He not only fears his creation but he realizes that at any moment, the monster might appear and do something horrific.
This is for Frankenstein.