Installing New Add-ons
Add-ons that are not part of a Mathematica distribution are typically installed in the directory specified by the Mathematica global variable $BaseDirectory. Add-ons intended for one particular user are typically located in the user-specific directory specified by $UserBaseDirectory. To see the exact location for either of these directories, evaluate $BaseDirectory or $UserBaseDirectory. See A.8.2 for more information.
Add-ons can be installed in either the Applications or Autoload subdirectories of $BaseDirectory or $UserBaseDirectory. Add-ons installed in the Autoload subdirectory are automatically loaded when the front end and kernel are started (see Autoloaded Add-ons). Add-ons installed in the Applications subdirectory can be loaded manually when needed (see Using Add-ons).
If an add-on is installed in $BaseDirectory, the application is available to all users. If it is installed in $UserBaseDirectory, the application is available only to that user.
Installing An Add-on
To install an add-on, copy it into either the Applications or Autoload subdirectories of $BaseDirectory or $UserBaseDirectory. If it came as an installer archive, it should come with instructions on unpacking the files. Otherwise, you can simply copy the add-on directory as you would any other directory.
After installing the files, use the Rebuild Help Index command in the Help menu. This tells the front end to add any help files that the add-on may contain and to incorporate them into the Help Browser's categories and index. These files will be then accessible in the Add-ons section of the Help Browser. Open the Help Browser and click the Add-ons button. The add-on's help files will be listed under the add-on's name at the bottom of the left-hand column.
Add-ons installed in the Autoload subdirectory will be loaded automatically on startup by both the kernel and the front end.
Ordinarily a package will declare one or more functions in the kernel. In order to save time and memory on startup, these functions are usually declared as function stubs; the full package is loaded when one of the functions is used for the first time.
An add-on may also install new menu items or evaluators in the front end, or reset configuration options in the front end. Check the documentation for the add-on to find out about any changes it makes to the front end.
Installing pre-3.0 Packages
If the add-on you are installing is not optimized for Version 3 or later, the Help Browser will not be able to display its help files, but you can still open the help files manually by using the Open menu command in the ordinary way.
If the add-on does not contain the files necessary for it to be autoloaded, it makes no difference whether it is installed in the Applications or Autoload subdirectory.