@Melphyx, No need to put them in a specific folder.
- Unzip and place the files in any folder.
- On the timeline, drag one clip over another to create a transition.
- Select the transition (purple box), then click the properties tab.
- Navigate the drop-dpwn menu (where it says “dissolve”) to the bottom of the list (“custom”).
- Navigate to the folder in step 1 and click on one of the png files.
- Play the transition.
Ta- dah, your transition should now appear.