Just select (copy) your whole manuscript starting with Chapter 1 and paste it into Chapter 1 of Dabble. This should make importing much easier!
When you paste content into Dabble, it will look for scene breaks and chapter headings. If they are detected, it will automatically create the chapters and scenes for you.
A chapter will be the text "Chapter 1: This is a chapter title" on a line by itself, or "Chapter 1 [newline] This is a chapter title" where the title is directly after the chapter number. (If you don't have a chapter title it will still work).
A new scene in a chapter is recognized by either "#" or "***" on a line by itself.