Step 1 

Go to "Video on-Demand" page.

Step 2

Click "Edit video settings".

Step 3 

Click "Advertisement".

Step 4 

Select advertisement video and enter its information. 

Step 5 

Click "Add Pre-Roll video" button.

Step 6 

Click "Save" button.Here is

Here is an example i added two advertisement to my video.

Now to see your advertisements.
Click on your video to open player page.
In player page each advertisement will play on its start time and you can skip it after skip time.

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