Well, first check if it's on any of the major streaming services you subscribe to. If not, try looking at the official website of the movie producers or distributors. They might have information on where it can be watched, either directly on their site or through a partnered streaming service. Another option is to check with your local video rental stores, although they are not as common these days.
I'm not sure as I haven't read the story specifically. But it could be characters who are initially normal humans until they discover their immortality. Maybe there's a scientist who accidentally stumbles upon the secret of eternal life and becomes one of the main characters.
Perhaps it's about the struggle with time. If we can never die, time becomes an endless expanse. The story could show how the characters deal with the monotony or the ever - changing nature of a world where they are eternal. They might have to adapt to seeing civilizations rise and fall around them while they remain unchanged.
You can try checking popular streaming platforms like Netflix or Amazon Prime Video. Sometimes it might also be available on cable TV channels that focus on movies.
You can also use a recursive narrative structure. Start with a basic story and then keep adding new layers or versions of the same story within it. Like a story within a story within a story. This can give the feeling of it never really ending. Another approach is to base the story on an eternal concept such as the cycle of life and death, where the story can keep following different characters through their life - death - rebirth cycles.