Create a slicer in an existing PivotTable

1. Click anywhere in the PivotTable for which you want to create a slicer.
2. On the Analyze tab, click Insert Slicer. In older versions of Excel, click the Options tab, and then click Insert Slicer.
3. In the Insert Slicers dialog box, select the check box of the PivotTable fields for which you want to create a slicer.
4. Click OK.A slicer is displayed for every field that you selected.
5. In each slicer, click the items on which you want to filter.
   

Reference : https://support.office.com

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