Hello,
there currently is no such feature that you can export a process from Alfresco Activiti and import it into Alfresco Community Edition to be executed. There is an UI integration module available for the Enterprise Edition that provides transparent access to Alfresco Activiti processes within the UI of the local Alfresco Enterprise Edition server, but I believe Alfresco Activiti must be installed on the same server for that.
Currently, Alfresco Activiti is a seperate product to Alfresco ECM (Community / Enterprise Edition) and developed as such, i.e. it uses a different UI technology and a seperate roadmap. As far as I understand, integration of the two is part of the main focus, but integration will likely keep prioritizing ReST API and UI integration rather than export/import functionality between the two.
Regards
Axel