itch.io

I am adding custom collections to the [application]/Collections folder, and restarting AssetForge, but they don't appear in the arrow-selectable list. I know somewhere it says how to do this on a Mac, ("launch from itch.io"), but being completely explicit would be very helpful. I installed the application on the Mac purely by unzipping the downloaded file, and executing the application from within there. I am not familiar with the itch launcher. Other than the custom Collections, things seem to be working great. Thank you!