If the thing to do is create the main character. These characters need a defining set of traits and backstories. Write a summary of each character. When designing a character, you might ask yourself questions like:
What does your character look like?
What is the character's name?
What kind of personality does the character have?
Where did that character come from?
Does your character have special powers or abilities?
Is the character a hero or a villain?
What is the nature of your character's relationships with other characters?
Think about what you want your character to accomplish. Each character should have a goal. If you understand the main character's purpose, the story development will reflect that and you can read it smoothly. Without a clear goal, characters can drift out of the story or seem pointless. Remember that your characters' goals are what drive the action in your story, and what forces them to act.
Make your characters interesting and memorable. Create original and complex characters. There are several ways to achieve this goal:
Conflict characters as the story naturally progresses
Let your character wander from the path of least resistance
Put your character into conflict or dangerous situations
Let your character struggle and learn from that struggle
Introducing an emotional or awkward character
Give your character lots of action
Create a character that is contradictory to yourself.