There are two ways to create new chapters and scenes while working in First Draft Pro:
Create chapters and scenes on the outline
Create chapter and scene breaks while writing, directly in your manuscript
Add new chapters by clicking on the "Add Chapter" button on the outline:
Add new scenes by clicking on the "Add Scene" button on each chapter:
Create a chapter or scene break while you are writing by clicking at the point where you want to create the break, and selecting the button to split a scene or chapter:
You can also use a shortcut to create scenes and chapters in the manuscript:
Ctrl-enter creates a scene break
Alt-enter creates a chapter break