Since Jira Agile is an add-on extension to Atlassian Jira, you will need a running installation of Jira. You can download and install the latest version of Jira at http://www.atlassian.com/software/jira/download.
Jira and the additional add-on Agile Cards for Jira, used in Chapter 5, Customizing Jira Software, can be downloaded and installed them from inside the Jira application. However, if your Jira installation does not have access to the internet, you can download Jira Agile from https://marketplace.atlassian.com/plugins/com.pyxis.greenhopper.jira and Agile Cards for Jira from https://marketplace.atlassian.com/plugins/com.spartez.scrumprint.scrumplugin.