How to pass report id dynamically to a custom widget

Summary:

I have created a configuration setting which contains all report ids needed. I need to show the report in customer portal using this config setting. There is a custom widget. In that how to fetch report id and how to pass report id?

Content (required):

Version (include the version you are using, if applicable):

21C

Code Snippet (add any code snippets that support your topic, if applicable):

This is the code which iam using:

$reportcfg = \RightNow\Utils\Config::getConfig(CUSTOM_CFG_REPORT);

$reportcfg = json_decode($reportcfg, true);

$reportID = $reportcfg['product']; 

in $reportID iam getting report id from config setting. But how to use this id in widget?