README: Update and add usage section

README.rst

@@ -9,9 +9,52 @@ This repository contains KiMesh, a KiCAD pcbnew plugin that generates security m
 
 Installation
 ------------
-To install, copy the "kimesh" directory into your KiCAD installation's scripting plugin folder. Usually, this is
-`~/.config/kicad/scripting/plugins/` for KiCAD stable installations or `~/.config/kicad/5.99/scripting/plugins/` for
-nightly builds. On Windows, these paths can be found in your user account's `AppData/Roaming` directory.
+
+KiMesh has two parts: The pcbnew plugin that generates the traces, and the magic footprints that you use to tell the
+plugin how many traces of which dimensions to generate where.
+
+To install the plugin, copy the "kimesh" directory into your KiCAD installation's scripting plugin folder. Usually, this
+is `~/.config/kicad/scripting/plugins/` for KiCAD stable installations or
+`~/.config/kicad/[major version].99/scripting/plugins/` for nightly builds. On Windows, these paths can be found in your
+user account's `AppData/Roaming` directory.
+
+To install the footprint libraries, the easiest way is to download the library zip from the project's repo
+`[link] <https://git.jaseg.de/kimesh.git/plain/mesh_footprints.tar.xz?h=main>`__, unpack it to your project folder, and
+add the unpacked libraries as project-specific libraries through KiCad's library management thingy.
+
+Usage
+-----
+
+To work, KiMesh requires four things:
+
+1. An area free of other features such as footprints or traces where to generate the mesh.
+2. One or more "graphic polygons" on a drawing layer that specify the area of the mesh.
+3. A closed board outline on the `Edge.Cuts` layer.
+4. One of the magic footprints from the KiMesh anchor library that defines the mesh's number of wires and their
+   dimensions, and tells KiMesh where to start the mesh and in which direction to start it.
+
+You can choose any layer for the outline polygons, such as the pre-defined `User.Eco1` or `User.X` layers, or you can
+define your own. You just have to select that layer later in KiMesh's generator dialog. Note that KiMesh only processes
+graphic polygons on that layer, and ignores other shapes such as lines, rectangles or circles. You can still use other
+shapes, but you have to manually convert them to polygons before running KiMesh. To convert other shapes to
+a polygon, select them, open the context menu with a right click, then choose the "Create from Selection 🞂 Create
+Polygon from Selection" entry. For rectangles or circles, use the "Use Centerlines" option. For lines or arcs, use the
+"Create bounding hull" option.
+
+Place the magic anchor footprint on the outline of the mesh's shape polygons so that you have space to route out the
+traces. The anchor footprint has an arrow on the `F.Fab` layer that indicates in which direction the mesh will be
+generated.
+
+I recommend adding the mesh to the schematic with one of KiCad's built-in `Connector_02xN_Top_Bottom` footprints. For a
+mesh with k wires, choose a symbol with two rows of 2k pins each. For instance, for two mesh wires, choose
+`Connector_02x04_Top_bottom`. Then assign one of the magic footprints to that symbol. To avoid DRC warnings, join the
+two halves of the mesh on the output side of the footprint. That's the right side in default orientation, where the
+higher-numbered pins are.
+
+.. image:: screenshot-mesh-schematic.png
+   :width: 800
+   :alt: A screenshot of the connector footprint mentioned in the previous paragraph, shown conencted up as described in
+         KiCad's schematic editor.
 
 Theory of operation
 -------------------