There's been loads of threads asking about this lately.
It's all about the quicksave/autosave system.
1. In your first playable scene you should create an at begin of scene action.
2. add pause 500ms > if autosave #0 exists > else > execute autosave #0 > end if > pause 1000ms > now whatever other actions you want it to trigger. What you have done there is checked if autosave #0 exists & if it doesn't then create it. The pause after prevents it from triggering any other actions / conditions so that it gives it enough time to write the raw data to the save file before anything is changed.
3. In your new game button if you don't trigger any cut-scenes / menu scenes or videos before the first playable scene, you should add an if query to it. If autosave #0 exists load autosave #0 else change to x scene (whatever it needs to do) then add an end if action part.
This may vary a bit depending on how your game starts. But that's the basic grasp of it. The autosave system is also useful for creating the resume / continue system.