Do a Save As so the file is in good order.
Add any extra pages you will need at the beginning or
end of the document. Remember that the total number of pages must be a multiple of four.
Usually the covers and inside covers are in a separate file and are not part of the
imposition process.
If you will be using the automatic Table Of Contents
method, this must be done before you impose.
Goto Utilities Menu/Plugins/Build Booklet
Remove any extra pages from the end of the file by
selecting them in the list and clicking Delete
Layout should be set to 2-up Saddle Stitch,
don't use Creep, turn on Guides in Gutter
It will ask you if you want to save it again, that is
OK
When it is done you will have a new, untitled file
that is imposed a ready to print - Save it under a new name - the old filename plus the
words "(imposed)" at the end