Video Digitizing (Add transisitions)
Left Click & hold on selected transition to drag it into the transition area.
The red area below the light grey workarea indicates that rendering is required.
Go to File > Save to save your project before rendering.
Press "Enter" (located on keyboard) to start rendering.
You will see a "Building Preview" window which shows you how long the process will take.
Once the rendering is done, the red area under the light grey workarea bar will turn green.
You will then be able to preview your video with the transition effect in it.