Reorganised and update install instruction in the docs

docs/source/usage_notes.rst

@@ -0,0 +1,47 @@
+.. _a_notes:
+
+*************
+Project Notes
+*************
+
+novelWriter doesn't have a database and complicated forms for filling in details about plot
+elements, characters, and all sorts of additional information that isn't a part of the novel text
+itself. Instead, all such information is saved in notes. The relation between all these additional
+elements is extracted from the documents and notes by the project indexer, based on the tags and
+references you set within them.
+
+Using notes is not required, but making at least minimal notes for each plot element, and adding a
+tag to them, makes it possible to use the :guilabel:`Outline` feature to see how each element
+intersects with each section of the novel itself, and adds clickable cross-references between
+documents in the editor and viewer.
+
+
+.. _a_notes_tags:
+
+Tags in Notes
+=============
+
+Each new heading in a note can have a tag associated with it. The format of a tag is
+``@tag: tagname``, where tagname is a unique identifier. Tags can then be referenced in the novel
+documents, or cross-referenced in other notes, and will show up in the outline view and in the
+back-reference panel when a document is being viewed.
+
+The syntax highlighter will alert the user that the keyword is correctly used and that the tag is
+allowed, that is, the tag is unique. Duplicate tags should be detected as long as the index is up
+to date. An invalid tag should have a green wiggly line under it, and will not receive the syntax
+colour that valid tags do.
+
+The tag is the only part of these notes that the application uses. The rest of the document content
+is there for the writer to use in whatever way they wish. Of course, the content of the documents
+can be exported if you want to compile a single document of all your notes, or include them in an
+outline.
+
+A note can also reference other notes in the same way novel documents do. When the note is opened
+in the view panel, the references become clickable links, making it easier to follow connections in
+the plot. Notes don't show up in the outline view though, so referencing between notes is only
+meaningful if you want to be able to click-navigate between them.
+
+.. tip::
+   If you cross-reference between notes and export your project as an HTML document using the
+   :guilabel:`Build Novel Project` tool, the cross-references become clickable links in the
+   exported HTML document.