You don't. At least not as in other rulesets.
What I do when I write down my stories, is to include links to the enemies my players will be facing, in the story text. So each is easy to drag and drop into the combat tracker. And since positioning on a map isn't a thing in the Genesys system, it really isn't that much of a deal. This is very much theater of the mind.
Hope that helps
Vires Animi