here is some information about charting in general:
http://www.splunk.com/base/Documentation/latest/User/UseReportingCommands
and it sounds as though you might also find the Splunk Tutorial useful:
http://www.splunk.com/base/Documentation/latest/User/WelcometotheSplunktutorial
this tutorial walks you through how to use Splunk, including how to create reports.