Go to "Video on-Demand" page.
Click "Edit video settings"
Click on "Bookmarks"
While the video is playing click "Add bookmark" in the second you want.
Enter your bookmark title.
Click "Save" button.
For example i added two bookmarks for my video.
Now to see your bookmarks.
Click on your video to open player page.
In player page in section bookmarks you will find them.
When you select any one of them the video will go to the related second.
If you cannot see bookmarks section go to your settings to show it.
To know more about player admin settings click here.