First you need to upload the plugin in your hosting server.
Uncompress the plugin named activehelper-livehelp.zip in the default wordpress plugin directory "\wp-content\plugins"
Login in your wordpress admin area and go to plugins.
By clicking in the option activate bellow the plugin name "ActiveHelper LiveHelp" you can install the plugin.
The installation process will be take a few moments and when finished you can see the plugin activated.