As a beginner, I'm having trouble trying to write an epilogue for my dystopian story. I don't know where to start. Can you help me?

Why do you need one?

The vast majority of novels don’t have either a prologue or an epilogue.

Nor do they need them.

The only time I ever use an epilogue is when I need to add a short 3rd person chapter to a first person book, where a completely different group of people are setting a scene for a latter book in the series.

Typically that’s a group of higher beings reporting on what happened to someone, planning what’s coming next, and just telling the reader there’s something else going on, without hinting at what it is.

The last time I did one was about 15 novels ago.

You put an epilogue on the end only if there is something you need to end with that isn’t part of the main story, but needs to be said.

If it is part of the story, then it’s not an epilogue, just another chapter.

Even if some time elapses, it’s still another chapter, not an epilogue.

The fact this is coming hard to you probably means you shouldn’t be doing one.

E2A: The first time I did this was after I had a character exit the story abruptly with everyone thinking she was dead. But on reflection, I didn’t want to leave it there. I added a chapter as an epilogue set 2 years later. Some 40 odd novels later, the timeline caught up, and I built that epilogue into that current book, by building around what had already been said.

Sometimes they work. Most times, they’re not needed.