Hi,
have you looked into this step-by-step in the documentation of creating a custom filter?
docs.kentico.com/.../developing-custom-filters
This also includes the part where you register your filter: 'Adding the filter to a portal engine page'
You use a Kentico Filter Web Part and point it to your custom file
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You could also create your own Filter Web Part, you might want to look in the Dancing Goat sample site to see Kentico samples.