Add property to DAM Asset metadata using custom workflow

You can get required details like below

//Get session

Session session = workflowSession.getSession();

// Get the Workflow data (the data that is being passed through for this work item)

final WorkflowData workflowData = workItem.getWorkflowData();

// Get the path to the JCR resource from the payload

        final String payloadPath = workflowData.getPayload().toString();

        ResourceResolver resourceResolver = null;

        try {

            // Get the ResourceResolver from workflow session

            resourceResolver = getResourceResolver(workflowSession.getSession());

            Resource resource = resourceResolver.getResource(payloadPath);

            // Using resource, we can read/update/add properties to required node by adapting to node or iterating to the required node and save the node by using session

        }catch(Exception e){

        // Add appropriate logger statements for checking errors

        }

Hope this helps!