To rent any of the ChessCube streaming videos, simply open the in-application store and click on the video tab:
After confirming your order, the video will load up in the background. From there you can watch it. To jump chapters, hit the "Next" button:
If you're returning to watch a video that you've previously purchased, simply go into your inventory, hit the "Video" tab, and choose your video:
Have fun and enjoy!