Use the Scenarios window of the ATG Control Center to create a scenario that listens for community proposal creation events and starts the community proposal workflow.

A simple scenario to start a workflow might look like this:

The scenario starts with the creation of a community proposal. The scenario listens for CommunityProposalMessages. A CommunityProposalMessage includes the CommunityProposal as a property. Given the CommunityProposalMessage, the scenario starts a workflow, assigning the id property of the CommunityProposal as the subject ID of the workflow.