Indeed tutorials on the wiki are a little outdated, since we were very busy working on the 2nd version of PopcornFX.
You can check out our open beta: https://www.popcornfx.com/services/editor-v2/
You will have to registrer in order the try the new nodal editor.
Collisions events are generated by the physics evolver, by default, the event is name "OnCollide".
To use that event, you just have to add in the "Events" section, the name of the event, and the path of the effect you want to spawn (eg: a local effect created in the "LayerGroups").
Some images to explain.
You can also dowload the tutorial package from the launcher and open TrailsCollide.pkfx to look closer how it works if you want.
If you want to collide with a custom shape, look at this. It's almost the same process.
Hope this help,