You can add a filter node after any activation node. The guest will be allowed to choose one of the filters you've added to the node.
You can select from any or all of the pre-loaded filters by clicking on the ones you want to include. In the image below, the two filters on the right are selected. Include the "None" square if you want guests to have the option not include a filter.
Finally, select your filter screen layout from the lower carousel.
Questions? Contact firstname.lastname@example.org