In 1984, in what ways is Oceania a totalitarian state?
There is certainly enough evidence for you to identify, even just by reading the first chapter, that would suggest that Oceania is a totalitarian state. This is one of the central themes of this terrifying novel after all. You might want to think about the sense of fear and suspense that is created in the first chapter as Winston Smith describes a world where the citizens live in constant fear and are watched all the time:
The black-mustachio'd face gazed down from every commanding corner. There was one on the house-front immediately opposite. BIG BROTHER IS WATCHING YOU, the caption said, while the dark eyes looked deep into Winston's own... In the far distance a helicopter skimmed down between the roofs, hovered for an instant like a bluebottle, and darted away again with a curving flight. It was the police patrol, snooping into people's windows. The patrols did not matter, however. Only the Thought Police mattered.
This is one small example from the novel that shows how Big Brother is not just content with having power - he wants to have power over every single one of his citizens, going into their very homes, lives and minds, to try and dominate them and control them. They are constantly watched and live out their lives in constant fear.