When you enter the main menu, in the upper right side you'll see a small window, written in it "Default player", and above it there is a small head.
Click on the head, and a window will be openned, allowing you even to play with your own created CAS sim. The new player will start a new story, overriding the default player.
I played several times with Jessica, but I didn't like the aspiration of the male (fortune). So I created me a new CAS sim, and restarted the game.
By the way, I suggest you to choose a male sim, preferably Pisces, because there is a castaway female on the second island, who waits to be matched...
