1. Write two Aspects. One High Concept and one Trouble.The High Concept is the basic definition of your character. Something like "Hotshot Daredevil" or "Freelance Exorcist" or something similar. You may also want something that is a little more flavorful, but for a one-shot game, simple explanations are fine.
A Trouble is something that gives you difficulties in life. This could be a physical problem such as a bad leg, a personality quirk that leads you into bad situations or a particular enemy or obsession. Something like "Pyrokinetic Episodes" indicating someone who has trouble controling their fire-starting abilities or "Rash Arrogance" for someone who tends to rush in without thinking and be overconfident about their abilities.
2. Write another Aspect.Create another Aspect related to a special ability or fact about you. This could be related to an important friend, a special talent or psychic ability.
3. Give your character a name and decide what they look like.This is basically just deciding on your character name and description.
4. Choose your approaches.There are six "approaches" in Fate Accelerated that replace characteristics and skills. They are:
You get one approach at +3, two at +2, two at +1 and one at +0.
5. Set Refresh to 3This is represents how many Fate Points your character starts the session with.
6. You may write up to two more Aspects and create 1 Stunt. This is optional.You can wait on this until later in the session. For example, "Wait, can I say my character has Been in Tougher Spots as another Aspect and spend a Fate Point on that for a +2?"
In the Dunadan of Avalon scenario, you will use one of these extra Aspects to represent your chosen upright model.
As for Stunts, you get 1 for free that can also be chosen later. Stunts represent areas where you have special capabilities or skills. There are two types, one where the character gains a bonus in certain situations and using certain approaches. And one where the character gets a 1/session ability to make something happen.
"Because I'm a Hotshot Daredevil Pilot I get a +2 when Flashily Creating an Advantage while piloting a vehicle."
"Because I'm an Experienced Freelance Exorcist I get a +2 when Carefully rolling an Overcome action to remove a curse."
"Because I have Chi-Enhanced Reflexes, once per session I can choose to go first in a physical confrontation."
"Because I am the Demon of the Sun, once per session I can downgrade one Consequence while standing in sunlight."