You would like to show the Case Merge Premium Duplicate Detector in the Case Feed View

To add the Duplicate Detector to the Case Feed View, it is recommended you create a custom Visualforce page to display the duplicate detector in the Feed View using the following steps.

1. Navigate to Setup --> Develop --> Pages and click New
2. Configure the page as follows:
   • Label: Duplicate Cases
   • Name: Duplicate_Cases
   • Description: Custom page to display the Case Merge Premium Duplicate Detector
   • Visualforce Markup: 

     • <apex:page standardController="Case" showHeader="false" standardStylesheets="true" > 
       Duplicates: <apex:iframe src="/apex/csmrgp__CsMrgDupeDetector?id={!case.id}"/> 
       </apex:page>
       

3. Click Save.
4. Navigate Setup --> Customize --> Cases --> Page Layouts and click Edit to any Feed Based layout where you want to add the Duplicate Detector.
5. Click Feed View and scroll to the 'Other Tools and Components' subsection
6. Under Custom Components click 'Add a Visualforce page'
7. In the Lookup dialog search box enter 'Duplicate Cases' and click Go. 
8. Click on Duplicate_Cases and set the Height field to 30
9. Under Choose Placement, move Duplicate Cases from Hidden to the Right Column and move it to the desired position in the list.
10. Click Save.

A visual demonstration of the steps above can be accessed by clicking the link below:
https://youtu.be/qlzAZ_dsztU