You could start by listening to people's personal ghost experiences. When you hear real - life accounts from those you trust, it can make you more likely to believe in ghost stories. Also, visiting places that are said to be haunted can have an impact. Standing in a spooky old building and feeling the strange atmosphere can start to make you think that there might be something more to those ghost stories.
To start believing in ghost stories, first, don't be too rational all the time. Let your imagination run wild a bit. Watch some good horror movies based on ghost stories, not just for the scares but to understand the concepts behind them. Then, try to research some historical ghost stories, like those from old castles or cemeteries. You might find that there are common themes and elements that seem to suggest there could be some truth to these stories. Also, engage in conversations with people who are believers. They can share their thoughts and experiences, which may gradually change your perspective and make you more open to believing in ghost stories.
One can start by reading a lot of classic ghost stories. They often have detailed descriptions and spooky elements that can make you more open to the idea.