How to use the VSE Transitions pack?

After downloading the 2.3 Gb .zip file you extract the folder on a place you easily remember. Then in the VSE you can add a strip. Here the steps: 

1. Have a background and a foreground image or video. 
2. Put the foreground on layer 4, the background on layer 2.
3. Add a transition on layer 3.  (Shift+A > Image/Sequence)
4. 
5. Above, you see that the middle layer is the layer with the transition mask. 
6. Select the transition layer, the middle one and in the properties panel you go to tab called Strip. There you set the Blend on Alpha Under. See screenshot below:
   
7. At the bottom in the screenshot above, you see Reverse Frames. You will want to use that most of the time. So you can switch that on as well. 
8. Now select the top layer, and in the Properties Panel you click on tab Modifiers. 
9. In the drop down called Add Strip Modifier, you select Mask.
10. Click in the Text Field behind mask, and select the strip that contains the transition.
11. Move the timeline to see the effect. 

TIP: you can also masks in Modifiers. When you add a modifier like brightness/contrast you see an option to add a mask layer in there as well. You could use multiple transition layers and decide what it should affect.