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
You could also create your own Filter Web Part, you might want to look in the Dancing Goat sample site to see Kentico samples.