A preroll is a video that is used to play before another video. Any video on your Media Manager account can be used as a preroll and can be set via the edit popup.
Firstly open up the edit popup on the video you wish to attach a preroll to by right clicking or clicking the options icon.
Next click on "Details" to open up the edit popup and click the "Preroll" tab.
You can then select from the list, the video you wish to use as the videos preroll. Once selected the preroll options will show.
There are a couple of options you can use.
ONCLICK - This is the URL the viewer will be taken if they click on the preroll video.
SKIPPABLE - This determines if the video can be skipped. A message will appear in top right hand corner with a countdown. If this option is selected, then a skip button will also appear.
SKIPPABLE AFTER - This is the time (in seconds) after which the skip button will appear and the viewer can skip.