In /administrator, go to Extensions > Manage > Install. Browse for the package you downloaded and press the install button. You should soon see a success message.
The package installs 2 plugins (System - EU e-Privacy Directive, and Ajax - EU e-Privacy Directive) and a module (mod_eprivacy). Although there are many configurations to be made, the first is enabling both plugins.
Browse to Extensions > Plugins and search for "privacy". You're looking for System - EU e-Privacy Directive, and Ajax - EU e-Privacy Directive - click the red X on each plugin to enable them. At this point, you're ready to begin configuring the extensions.