The Particle Replacement window allows you to configure a layer to render its content as particles created by Particle Designer and compatible external particle systems.

While using this option, be sure your particle image file has the same name of the JSON file and resides in the same folder. Kwik will import the image file based on the particle file name and location. Select the layer you want to add the Particle feature and click the Particle replacement. The following window appears:

Browse your folders and point to the particle File (.json) created by your system.

If you have a payed Pro license of Kwik, you may see an option to create or edit your particles. Click the red fired icon

Particle Editing (Kaboom)

The tutorial is here