A premise statement (read the link, it is short) is not typically IN your story at all, not before it, not in the prose.
As the link says:
Every story has one premise. Only one. This premise is the underlying idea of your story-the foundation that supports your entire plot.
If you can establish what your premise is at the beginning of your project, you will have an easier time writing your story. That”s because the fundamental concept you create in advance will drive the actions of your characters.
I disagree with this notion that every story has a premise and ONLY ONE premise, but certainly you can devise a plot around some premise and devise perfect characters to populate that plot.
But you don't put the premise INTO the story, it is only a tool for the author to maintain consistency and stay on track when writing the story.