The idea is you can enter any tree by the base template - Athlete, in the top center here - of you have the points required (1) and meet the prerequisite (have either Athletics or Move already). You pay the point cost and take all the skill ranks and any Edge given by the template. The Athlete template serves as the prerequisite for any template with arrows leading from it to that other template (Star Athlete, Stunt Man, or Circus Performer) so you only need to pay the point cost for those templates.
From there you can continue on, taking any other template on this tree in the same manner, or you can take the base template on some other tree, so long as you have points to spend, and meet the prerequisite. This gives the character a flavor and back history, much like a Life Path.