Newbie - Document window

i am working on a book and for some reason the page does not fill the space so I have a wide margin. i have not discovered how to fix it so that the document fills the screen. Thanks.

The first thing to check is the ruler, using Cmd-R or Format/Show Ruler, and make sure the text you started with doesn’t have an unnecessary right-side indent. Beyond that there are a few things in Scrivener that can intentionally reduce line width as not everyone likes to read 20" long lines of text. Fixed width is one of those, you’ll find those settings in the Editor preference pane, middle-right side. While you are in that pane, also check the “Margins” settings to the left of the fixed width settings. These are to be clear just visual margins, nothing to do with output. Page View is the other feature that can narrow the text column, but naturally since that is showing a simulated piece of paper, it won’t fill the screen and that is the whole point of it. So you if that’s what you’re using, you may just want to switch out and use the regular editor instead, with the View/Page View/Hide Page View menu command.