You need to download amCharts files from: 
http://www.amcharts.com/download

At http://www.amcharts.com/download choose the 2.x amCharts Flash & JavaScript 
bundle to download.

From it you have to extrac the following files (they are at amcharts/flash):
* amcolumn.swf
* amline.swf
* ampie.swf

Place them in the charts_graphs/apis/charts_graphs_amcharts/downloaded</em> 
folder of Charts and Graphs module directly, without any folder structure inside 
the downloaded folder.

Sorry for the inconvenience, but there's really nothing we
can do about it due to licenses restrictions and Drupal policy
to not ship anything non-GPL with the module code.

CAUTION: Do NOT assume you don't need swfobject.js since
charts_graphs already requires swfobject Drupal module. Unfortunately,
the versions of the two js files are different, so you can
not re-use swfobject from the module file for amCharts the way
you can re-use it for OFC2.