If you're running the latest version of Appcelerator Studio, then Alloy should be installed for you when you run Studio for the first time. However, if you want to install it manually, or if you're running Titanium as open source with your own IDE, then you can install Alloy from the terminal.
These chapters are going to assume that you're using OS X. However, you can do all of this using Windows too.
Typically, when you install Appcelerator Studio, it will install the mobile SDK and any add-ons, including Alloy. You can check whether Alloy is installed by typing the following in a terminal window:
$ alloy -v
This will return the version that is currently installed. If you don't have ...