Making writing fiction fun can involve giving yourself the freedom to be creative. For example, don't worry too much about getting everything perfect in the first draft. Just enjoy the process of telling the story and see where it takes you. You could also share your work with others and get their feedback, which can be really motivating.
Set realistic goals and give yourself rewards when you reach them. Also, don't be too hard on yourself if you have a slow day. Making writing a fun challenge rather than a chore helps a lot.
To make story time fun, try to act out parts of the story or have some interactive elements where the listeners can guess what's coming next. Also, choosing stories that are full of adventure and surprises helps a lot.