DAS cluster agent comprises of a DAS Webapp and an Event Processor. These components are installed on the Ambari cluster to use with DAS. Additionally, you can install the DAS-DP App within the DP environment, and it communicates with the DAS components within the cluster.
Following is a block diagram showing the various components in a typical DAS deployment:
The DAS Webapp serves the DAS UI, and it should be on a machine that is accessible to your end users, or you should have a proxy setup to access the DAS UI.