@Rajkumar Bommal 

var scriptName = new <Script Include name>();
var storeValue = scriptName.<method name to execute>(<arguments>);

Please check above syntax to call script include in custom actions.

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@Rajkumar Bommal 

simply call it like this in normal way how you call from any server side

var value = new ScriptInclude().functionName();

If my response helped please mark it correct and close the thread so that it benefits future readers.