Download the latest stable version from Activiti's website or you can check out the code from github and unzip to a directory of choice and then check out the readme.html that includes pointers to the docs and the release notes. The userguide ( docs/userguide/index.html ) includes instructions on ho...
Goto - http://www.jorambarrez.be/blog/2010/08/02/tutorial-a-bpmn-2-0-hello-world-with-activiti-5-0-alpha4-in-5-steps/
A very Good and detailed tutorial by Joram Barrez (one of the core Developer of Activiti)