Stories need characters readers will care about.
Writers need to get to know their characters, so the readers will also get to know them. Start by describing as much as you can picture. What is the hair color, eye color? How tall? Fat or fit? What is your character's favorite food? Sport? Music? Or does your character hate sports? Or like ancient chanting, while everyone around him loves bluegrass?
Pick a character from a book you love and describe him/her. This will show you the kind of details you need to know about your character to make him come to life.
You won't know your character all at once. You'll learn about him as you write, discover things you never thought of. Once you really know and care about your character, the odds are your readers will too.