Few options:
1. Events in AEM works on a change / modification in node or property [1], now If youe first workflow does any of these, then it will automatically trigger event listener. Inside event listener you can call Workflow process
[1] http://blogs.adobe.com/experiencedelivers/experience-management/event_handling_incq/
[2] https://helpx.adobe.com/experience-manager/using/events.html
[OR]
2. Based in property or node change done by first workflow you can create a workflow launcher which will call another workflow (would be simple and configurable)
3. Add a step in the end of Dam Asset Workflow which will executes another process step
Thanks