Add recipes for additional packages README in private/local dir

private/local/README.md

@@ -2,5 +2,34 @@
 
 The content of this directory is ignored by Git.
 
-This is the place to store the local packages that you define in
-the `dotspacemacs-additional-packages` variable of your dotfile.
+This is the place to store the local packages that you define in the
+`dotspacemacs-additional-packages` variable of your dotfile.
+
+Additional packages can be added using the same recipe as for [adding packages
+to layers](https://develop.spacemacs.org/doc/LAYERS.html#packagesel) i.e.:
+
+- For a local package:
+  - load the file explicitly, using the full path to the file, by placing a
+  `(require '~/.emacs.d/private/local/package-name)` within the body of the
+  `dotspacemacs/user-config` function of your dotspacemacs file.
+  - Alternatively create a directory with the name of the package in the
+  .emacs.d/private/local directory, and add that directory to the load-path
+  variable by adding `(some-package :location local)` to the list
+  `dotspacemacs-additional-packages` within the `dotspacemacs/layers` function
+  of your dotspacemacs file. After placing your package file into this
+  package-directory the file can be loaded, without requiring the full path, by
+  placing a `(require 'package-name)` within the body of the
+  `dotspacemacs/user-config` function of your dotspacemacs file.
+
+- If the package is on (M)ELPA simply add the package name to the list
+  `dotspacemacs-additional-packages` in your dotspacemacs file
+
+- for a package hosted on github the recipe for github packages can be used i.e. add
+
+```
+(some-package :location (recipe
+:fetcher github
+                             :repo "some/repo"))
+```
+
+to the list `dotspacemacs-additional-packages` in your dotspacemacs file.