This should be 250 words or more, including a description of both the physical and their personality.
If you are a channeller, think about whether you are a wilder (with a block) or a person with the spark inborn, or someone who just has the ability to learn.
If you are aiming to become a Warder, think about your character's level of experience in weaponry. With few exceptions, your character is very young and thus inexperienced. The training in the Warder Yards is meant to shape your character's skills from the beginning of their lives. The saying that it's hard to teach an old dog new tricks applies for mankind too.
You may write this either in-character as a short piece of fiction, or out-of-character as a biography.