First line indentation is a format setting that is handled with the rest of the formatting in the book preview screens. You can click the eye icon at the top right corner of any editing screen to access that previewer.

Indent and paragraph spacing are among the options you have for formatting, but it can't be done within the editor itself. Keep in mind when you go to the preview screen that any invisible characters you've entered (spaces, paragraph breaks, etc) may make things look distorted depending on the theme and format settings you select.