You only need to install the Technology Add-on (https://splunkbase.splunk.com/app/3457/) on your heavy forwarder; once installed, make sure you set up your input scheduled inside a data input.
The dashboard add-on (https://splunkbase.splunk.com/app/3492/) should be able to work when installed on an active indexer or search head.
Finally, make sure that your data input targets a known index; the default target index is "rapid7".
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